Transcript CSharp - Chapter 17, Files and Streams

1
Chapter 17 – Files and Streams
Outline
17.1
17.2
17.3
17.4
17.5
17.6
17.7
17.8
17.9
17.10
17.11
Introduction
Data Hierarchy
Files and Streams
Classes File and Directory
Creating a Sequential-Access File
Reading Data from a Sequential-Access File
Random-Access Files
Creating a Random-Access File
Writing Data Randomly to a Random-Access File
Reading Data Sequentially from a Random-Access File
Case Study: A Transaction-Processing Program
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17.2 Data Hierarchy
Sally
Black
Tom
Blue
Judy
Green
Iris
Orange
Randy
Red
Judy
Green
Judy
Field
01001010
1
bit
Fig. 17.1 Data hierarchy.
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byte (ASCII for J)
file
record
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17.2 Data Hierarchy
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……
n-1
end of file marker
Fig. 17.2 C#’s view of an n-byte file.
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17.4 Classes File and Directory
static Me tho d
De sc rip tio n
AppendText
Returns a StreamWriter that appends to an existing file or
creates a file if one does not exist.
Copy
Copies a file to a new file.
Create
Creates a file and returns its associated FileStream .
CreateText
Creates a text file and returns its associated StreamWriter .
Delete
Deletes the specified file.
GetCreationTime
Returns a DateTime object representing the time that the file was
created.
GetLastAccessTime
Returns a DateTime object representing the time that the file was
last accessed.
GetLastWriteTime
Returns a DateTime object representing the time that the file was
last modified.
Move
Moves the specified file to a specified location.
Open
Returns a FileStream associated with the specified file and
equipped with the specified read/write permissions.
OpenRead
Returns a read-only FileStream associated with the specified
file.
Returns a StreamReader associated with the specified file.
OpenText
OpenWrite
Fig. 17.3
Returns a read/write FileStream associated with the specified
file.
File c la ss m e tho d s (p a rtia l list).
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17.4 Classes File and Directory
static Me thod
De sc rip tio n
CreateDirectory
Creates a directory and returns its associated DirectoryInfo .
Delete
Deletes the specified directory.
Exists
Returns true if the specified directory exists; otherwise, it
returns false .
GetLastWriteTime
Returns a DateTime object representing the time that the
directory was last modified.
GetDirectories
Returns a string array representing the names of the
subdirectories in the specified directory.
GetFiles
Returns a string array representing the names of the files in
the specified directory.
GetCreationTime
Returns a DateTime object representing the time that the
directory was created.
GetLastAccessTime
Returns a DateTime object representing the time that the
directory was last accessed.
GetLastWriteTime
Returns a DateTime object representing the time that items
were last written to the directory.
Move
Moves the specified directory to a specified location.
Fig. 17.4
Directory c la ss m e tho d s (p a rtia l list).
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// Fig 17.5: FileTest.cs
// Using classes File and Directory.
using
using
using
using
using
using
using
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
System.IO;
Outline
FileTest.cs
// displays contents of files and directories
public class FileTestForm : System.Windows.Forms.Form
{
private System.Windows.Forms.Label directionsLabel;
private System.Windows.Forms.TextBox outputTextBox;
private System.Windows.Forms.TextBox inputTextBox;
private System.ComponentModel.Container components = null;
[STAThread]
static void Main()
{
Application.Run( new FileTestForm() );
}
// Visual Studio .NET generated code
// invoked when user presses key
private void inputTextBox_KeyDown(
object sender, System.Windows.Forms.KeyEventArgs e )
{
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// determine whether user pressed Enter key
if ( e.KeyCode == Keys.Enter )
{
string fileName; // name of file or directory
Outline
FileTest.cs
// get user-specified file or directory
fileName = inputTextBox.Text;
// determine whether fileName is a file
if ( File.Exists( fileName ) )
{
// get file's creation date,
// modification date, etc.
outputTextBox.Text = GetInformation( fileName );
// display file contents through StreamReader
try
{
// obtain reader and file contents
StreamReader stream = new StreamReader( fileName );
outputTextBox.Text += stream.ReadToEnd();
}
// handle exception if StreamReader is unavailable
catch( IOException )
{
MessageBox.Show( "File Error", "File Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
}
// determine whether fileName is a directory
else if ( Directory.Exists( fileName ) )
{
// array for directories
string[] directoryList;
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// get directory's creation date,
// modification date, etc.
outputTextBox.Text = GetInformation( fileName );
Outline
FileTest.cs
// obtain file/directory list of specified directory
directoryList = Directory.GetDirectories( fileName );
outputTextBox.Text +=
"\r\n\r\nDirectory contents:\r\n";
// output directoryList contents
for ( int i = 0; i < directoryList.Length; i++ )
outputTextBox.Text += directoryList[ i ] + "\r\n";
}
else
{
// notify user that neither file nor directory exists
MessageBox.Show( inputTextBox.Text +
" does not exist", "File Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
} // end if
} // end method inputTextBox_KeyDown
// get information on file or directory
private string GetInformation( string fileName )
{
// output that file or directory exists
string information = fileName + " exists\r\n\r\n";
// output when file or directory was created
information += "Created: " +
File.GetCreationTime( fileName ) + "\r\n";
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// output when file or directory was last modified
information += "Last modified: " +
File.GetLastWriteTime( fileName ) + "\r\n";
Outline
FileTest.cs
// output when file or directory was last accessed
information += "Last accessed: " +
File.GetLastAccessTime( fileName ) + "\r\n" + "\r\n";
return information;
} // end method GetInformation
} // end class FileTestForm
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Outline
FileTest.cs
Program Output
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// Fig 17.6: FileSearch.cs
// Using regular expressions to determine file types.
using
using
using
using
using
using
using
using
using
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
System.IO;
System.Text.RegularExpressions;
System.Collections.Specialized;
Outline
FileSearch.cs
public class FileSearchForm : System.Windows.Forms.Form
{
private System.Windows.Forms.Label directionsLabel;
private System.Windows.Forms.Label directoryLabel;
private System.Windows.Forms.Button searchButton;
private System.Windows.Forms.TextBox outputTextBox;
private System.Windows.Forms.TextBox inputTextBox;
private System.ComponentModel.Container components = null;
string currentDirectory = Directory.GetCurrentDirectory();
string[] directoryList; // subdirectories
string[] fileArray;
// store extensions found and number found
NameValueCollection found = new NameValueCollection();
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[STAThread]
static void Main()
{
Application.Run( new FileSearchForm() );
}
Outline
FileSearch.cs
// Visual Studio .NET generated code
// invoked when user types in text box
private void inputTextBox_KeyDown(
object sender, System.Windows.Forms.KeyEventArgs e )
{
// determine whether user pressed Enter
if ( e.KeyCode == Keys.Enter )
searchButton_Click( sender, e );
} // end method inputTextBox_KeyDown
// invoked when user clicks "Search Directory" button
private void searchButton_Click(
object sender, System.EventArgs e )
{
// check for user input; default is current directory
if ( inputTextBox.Text != "" )
{
// verify that user input is valid directory name
if ( Directory.Exists( inputTextBox.Text ) )
{
currentDirectory = inputTextBox.Text;
// reset input text box and update display
directoryLabel.Text = "Current Directory:" +
"\r\n" + currentDirectory;
}
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else
{
// show error if user does not specify valid directory
MessageBox.Show( "Invalid Directory", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
Outline
FileSearch.cs
}
// clear text boxes
inputTextBox.Clear();
outputTextBox.Clear();
// search directory
SearchDirectory( currentDirectory );
// summarize and print results
foreach ( string current in found )
{
outputTextBox.Text += "* Found " +
found[ current ] + " " + current + " files.\r\n";
}
// clear output for new search
found.Clear();
} // end method searchButton_Click
// search directory using regular expression
private void SearchDirectory( string currentDirectory )
{
// search directory
try
{
string fileName = "";
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// regular expression for extensions matching pattern
Regex regularExpression = new Regex(
"[a-zA-Z0-9]+\\.(?<extension>\\w+)" );
// stores regular-expression-match result
Match matchResult;
Outline
FileSearch.cs
string fileExtension; // holds file extensions
// number of files with given extension in directory
int extensionCount;
// get directories
directoryList =
Directory.GetDirectories( currentDirectory );
// get list of files in current directory
fileArray = Directory.GetFiles( currentDirectory );
// iterate through list of files
foreach ( string myFile in fileArray )
{
// remove directory path from file name
fileName = myFile.Substring(
myFile.LastIndexOf( "\\" ) + 1 );
// obtain result for regular-expression search
matchResult = regularExpression.Match( fileName );
// check for match
if ( matchResult.Success )
fileExtension =
matchResult.Result( "${extension}" );
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else
fileExtension = "[no extension]";
// store value from container
if ( found[ fileExtension ] == null )
found.Add( fileExtension, "1" );
else
{
extensionCount = Int32.Parse(
found[ fileExtension ] ) + 1;
Outline
FileSearch.cs
found[ fileExtension ] = extensionCount.ToString();
}
// search for backup(.bak) files
if ( fileExtension == "bak" )
{
// prompt user to delete (.bak) file
DialogResult result =
MessageBox.Show( "Found backup file " +
fileName + ". Delete?", "Delete Backup",
MessageBoxButtons.YesNo,
MessageBoxIcon.Question );
// delete file if user clicked 'yes'
if ( result == DialogResult.Yes )
{
File.Delete( myFile );
extensionCount =
Int32.Parse( found[ "bak" ] ) - 1;
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found[ "bak" ] = extensionCount.ToString();
}
Outline
}
}
FileSearch.cs
// recursive call to search files in subdirectory
foreach ( string myDirectory in directoryList )
SearchDirectory( myDirectory );
}
// handle exception if files have unauthorized access
catch( UnauthorizedAccessException )
{
MessageBox.Show( "Some files may not be visible" +
" due to permission settings", "Warning",
MessageBoxButtons.OK, MessageBoxIcon.Information );
}
} // end method SearchDirectory
} // end class FileSearchForm
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Outline
FileSearch.cs
Program Output
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// Fig 17.7: BankUI.cs
// A reusable windows form for the examples in this chapter.
using
using
using
using
using
using
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
Outline
BankUI.cs
public class BankUIForm : System.Windows.Forms.Form
{
private System.ComponentModel.Container components = null;
public System.Windows.Forms.Label accountLabel;
public System.Windows.Forms.TextBox accountTextBox;
public System.Windows.Forms.Label firstNameLabel;
public System.Windows.Forms.TextBox firstNameTextBox;
public System.Windows.Forms.Label lastNameLabel;
public System.Windows.Forms.TextBox lastNameTextBox;
public System.Windows.Forms.Label balanceLabel;
public System.Windows.Forms.TextBox balanceTextBox;
// number of TextBoxes on Form'
protected int TextBoxCount = 4;
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// enumeration constants specify TextBox indices
public enum TextBoxIndices
{
ACCOUNT,
FIRST,
LAST,
BALANCE
Outline
BankUI.cs
} // end enum
[STAThread]
static void Main()
{
Application.Run( new BankUIForm() );
}
// Visual Studio .NET generated code
// clear all TextBoxes
public void ClearTextBoxes()
{
// iterate through every Control on form
for ( int i = 0; i < Controls.Count; i++ )
{
Control myControl = Controls[ i ]; // get control
// determine whether Control is TextBox
if ( myControl is TextBox )
{
// clear Text property (set to empty strng)
myControl.Text = "";
}
}
} // end method ClearTextBoxes
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// set text box values to string array values
public void SetTextBoxValues( string[] values )
{
// determine whether string array has correct length
if ( values.Length != TextBoxCount )
{
// throw exception if not correct length
throw( new ArgumentException( "There must be " +
(TextBoxCount + 1) + " strings in the array" ) );
}
Outline
BankUI.cs
// set array values if array has correct length
else
{
// set array values to text box values
accountTextBox.Text =
values[ ( int )TextBoxIndices.ACCOUNT ];
firstNameTextBox.Text =
values[ ( int )TextBoxIndices.FIRST ];
lastNameTextBox.Text =
values[ ( int )TextBoxIndices.LAST ];
balanceTextBox.Text =
values[ ( int )TextBoxIndices.BALANCE ];
}
} // end method SetTextBoxValues
// return text box values as string array
public string[] GetTextBoxValues()
{
string[] values = new string[ TextBoxCount ];
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// copy text box fields to string array
values[ ( int )TextBoxIndices.ACCOUNT ] =
accountTextBox.Text;
values[ ( int )TextBoxIndices.FIRST ] =
firstNameTextBox.Text;
values[ ( int )TextBoxIndices.LAST ] =
lastNameTextBox.Text;
values[ ( int )TextBoxIndices.BALANCE ] =
balanceTextBox.Text;
Outline
BankUI.cs
return values;
} // end method GetTextBoxValues
} // end class BankUIForm
Program Output
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// Fig. 17.8: Record.cs
// Serializable class that represents a data record.
using System;
Outline
Record.cs
[Serializable]
public class Record
{
private int account;
private string firstName;
private string lastName;
private double balance;
// default constructor sets members to default values
public Record() : this( 0, "", "", 0.0 )
{
}
// overloaded constructor sets members to parameter values
public Record( int accountValue, string firstNameValue,
string lastNameValue, double balanceValue )
{
Account = accountValue;
FirstName = firstNameValue;
LastName = lastNameValue;
Balance = balanceValue;
} // end constructor
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// property Account
public int Account
{
get
{
return account;
}
Outline
Record.cs
set
{
account = value;
}
} // end property Account
// property FirstName
public string FirstName
{
get
{
return firstName;
}
set
{
firstName = value;
}
} // end property FirstName
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// property LastName
public string LastName
{
get
{
return lastName;
}
Outline
Record.cs
set
{
lastName = value;
}
} // end property LastName
// property Balance
public double Balance
{
get
{
return balance;
}
set
{
balance = value;
}
} // end property Balance
} // end class Record
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// Fig 17.9: CreateSequentialAccessFile.cs
// Creating a sequential-access file.
// C#
using
using
using
using
using
using
using
using
using
namespaces
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
System.IO;
System.Runtime.Serialization.Formatters.Binary;
System.Runtime.Serialization;
Outline
CreateSequential
AccessFile.cs
// Deitel namespace
using BankLibrary;
public class CreateFileForm : BankUIForm
{
private System.Windows.Forms.Button saveButton;
private System.Windows.Forms.Button enterButton;
private System.Windows.Forms.Button exitButton;
private System.ComponentModel.Container components = null;
// serializes Record in binary format
private BinaryFormatter formatter = new BinaryFormatter();
// stream through which serializable data is written to file
private FileStream output;
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[STAThread]
static void Main()
{
Application.Run( new CreateFileForm() );
}
Outline
CreateSequential
AccessFile.cs
// Visual Studio .NET generated code
// invoked when user clicks Save button
private void saveButton_Click(
object sender, System.EventArgs e )
{
// create dialog box enabling user to save file
SaveFileDialog fileChooser = new SaveFileDialog();
DialogResult result = fileChooser.ShowDialog();
string fileName; // name of file to save data
// allow user to create file
fileChooser.CheckFileExists = false;
// exit event handler if user clicked "Cancel"
if ( result == DialogResult.Cancel )
return;
// get specified file name
fileName = fileChooser.FileName;
// show error if user specified invalid file
if ( fileName == "" || fileName == null )
MessageBox.Show( "Invalid File Name", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
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else
{
// save file via FileStream if user specified valid file
try
{
// open file with write access
output = new FileStream( fileName,
FileMode.OpenOrCreate, FileAccess.Write );
Outline
CreateSequential
AccessFile.cs
// disable Save button and enable Enter button
saveButton.Enabled = false;
enterButton.Enabled = true;
}
// handle exception if file does not exist
catch ( FileNotFoundException )
{
// notify user if file does not exist
MessageBox.Show( "File Does Not Exist", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
}
} // end method saveButton_Click
// invoke when user clicks Enter button
private void enterButton_Click(
object sender, System.EventArgs e )
{
// store TextBox values string array
string[] values = GetTextBoxValues();
// Record containing TextBox values to serialize
Record record = new Record();
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// determine whether TextBox account field is empty
if ( values[ ( int )TextBoxIndices.ACCOUNT ] != "" )
{
// store TextBox values in Record and serialize Record
try
{
// get account number value from TextBox
int accountNumber = Int32.Parse(
values[ ( int )TextBoxIndices.ACCOUNT ] );
Outline
CreateSequential
AccessFile.cs
// determine whether accountNumber is valid
if ( accountNumber > 0 )
{
// store TextBox fields in Record
record.Account = accountNumber;
record.FirstName =
values[ ( int )TextBoxIndices.FIRST ];
record.LastName =
values[ ( int )TextBoxIndices.LAST ];
record.Balance = Double.Parse( values[
( int )TextBoxIndices.BALANCE ] );
// write Record to FileStream (serialize object)
formatter.Serialize( output, record );
}
else
{
// notify user if invalid account number
MessageBox.Show( "Invalid Account Number", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
}
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// notify user if error occurs in serialization
catch( SerializationException )
{
MessageBox.Show( "Error Writing to File", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
Outline
CreateSequential
AccessFile.cs
// notify user if error occurs regarding parameter format
catch( FormatException )
{
MessageBox.Show( "Invalid Format", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
}
ClearTextBoxes(); // clear TextBox values
} // end method enterButton_Click
// invoked when user clicks Exit button
private void exitButton_Click(
object sender, System.EventArgs e )
{
// determine whether file exists
if ( output != null )
{
// close file
try
{
output.Close();
}
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// notify user of error closing file
catch( IOException )
{
MessageBox.Show( "Cannot close file", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
Outline
CreateSequential
AccessFile.cs
}
Application.Exit();
} // end method exitButton_Click
} // end class CreateFileForm
Program Output
BankUI graphical
user interface
 2002 Prentice Hall.
All rights reserved.
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Outline
CreateSequential
AccessFile.cs
Program Output
SaveFileDialogue
Files and directories
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All rights reserved.
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Outline
CreateSequential
AccessFile.cs
Program Output
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All rights reserved.
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Outline
CreateSequential
AccessFile.cs
Program Output
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All rights reserved.
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Outline
CreateSequential
AccessFile.cs
Program Output
 2002 Prentice Hall.
All rights reserved.
35
17.5 Creating a Sequential-Access File
Ac c ount Numb er
First Na me
La st Na me
Ba la nc e
100
Nancy
Brown
-25.54
200
Stacey
Dunn
314.33
300
Doug
Barker
0.00
400
Dave
Smith
258.34
500
Sam
Stone
34.98
Fig. 17.10
Sa mp le d a ta for the p rog ra m of Fig. 17.9.
 2002 Prentice Hall. All rights reserved.
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// Fig. 17.11: ReadSequentialAccessFile.cs
// Reading a sequential-access file.
// C#
using
using
using
using
using
using
using
using
using
namespaces
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
System.IO;
System.Runtime.Serialization.Formatters.Binary;
System.Runtime.Serialization;
Outline
ReadSequentialAc
cessFile.cs
// Deitel namespaces
using BankLibrary;
public class ReadSequentialAccessFileForm : BankUIForm
{
System.Windows.Forms.Button openButton;
System.Windows.Forms.Button nextButton;
private System.ComponentModel.Container components = null;
// stream through which serializable data are read from file
private FileStream input;
// object for deserializing Record in binary format
private BinaryFormatter reader = new BinaryFormatter();
[STAThread]
static void Main()
{
Application.Run( new ReadSequentialAccessFileForm() );
}
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// Visual Studio .NET generated code
// invoked when user clicks Open button
private void openButton_Click(
object sender, System.EventArgs e )
{
// create dialog box enabling user to open file
OpenFileDialog fileChooser = new OpenFileDialog();
DialogResult result = fileChooser.ShowDialog();
string fileName; // name of file containing data
Outline
ReadSequentialAc
cessFile.cs
// exit event handler if user clicked Cancel
if ( result == DialogResult.Cancel )
return;
// get specified file name
fileName = fileChooser.FileName;
ClearTextBoxes();
// show error if user specified invalid file
if ( fileName == "" || fileName == null )
MessageBox.Show( "Invalid File Name", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
else
{
// create FileStream to obtain read access to file
input = new FileStream( fileName, FileMode.Open,
FileAccess.Read );
// enable next record button
nextButton.Enabled = true;
}
} // end method openButton_Click
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// invoked when user clicks Next button
private void nextButton_Click(
object sender, System.EventArgs e )
{
// deserialize Record and store data in TextBoxes
try
{
// get next Record available in file
Record record =
( Record )reader.Deserialize( input );
Outline
ReadSequentialAc
cessFile.cs
// store Record values in temporary string array
string[] values = new string[] {
record.Account.ToString(),
record.FirstName.ToString(),
record.LastName.ToString(),
record.Balance.ToString() };
// copy string array values to TextBox values
SetTextBoxValues( values );
}
// handle exception when no Records in file
catch( SerializationException )
{\
// close FileStream if no Records in file
input.Close();
// enable Open Record button
openButton.Enabled = true;
// disable Next Record button
nextButton.Enabled = false;
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ClearTextBoxes();
// notify user if no Records in file
MessageBox.Show( "No more records in file", "",
MessageBoxButtons.OK, MessageBoxIcon.Information );
}
Outline
ReadSequentialAc
cessFile.cs
} // end method nextButton_Click
} // end class ReadSequentialAccessFileForm
Program Output
 2002 Prentice Hall.
All rights reserved.
40
Outline
ReadSequentialAc
cessFile.cs
Program Output
 2002 Prentice Hall.
All rights reserved.
41
Outline
ReadSequentialAc
cessFile.cs
Program Output
 2002 Prentice Hall.
All rights reserved.
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Outline
ReadSequentialAc
cessFile.cs
Program Output
 2002 Prentice Hall.
All rights reserved.
43
Outline
ReadSequentialAc
cessFile.cs
Program Output
 2002 Prentice Hall.
All rights reserved.
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// Fig. 17.12: CreditInquiry.cs
// Read a file sequentially and display contents based on
// account type specified by user (credit, debit or zero balances).
// C#
using
using
using
using
using
using
using
using
using
namespaces
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
System.IO;
System.Runtime.Serialization.Formatters.Binary;
System.Runtime.Serialization;
Outline
CreditInquiry.cs
// Deitel namespaces
using BankLibrary;
public class CreditInquiryForm : System.Windows.Forms.Form
{
private System.Windows.Forms.RichTextBox displayTextBox;
private
private
private
private
private
System.Windows.Forms.Button
System.Windows.Forms.Button
System.Windows.Forms.Button
System.Windows.Forms.Button
System.Windows.Forms.Button
doneButton;
zeroButton;
debitButton;
creditButton;
openButton;
private System.ComponentModel.Container components = null;
// stream through which serializable data are read from file
private FileStream input;
// object for deserializing Record in binary format
BinaryFormatter reader = new BinaryFormatter();
 2002 Prentice Hall.
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// name of file that stores credit, debit and zero balances
private string fileName;
[STAThread]
static void Main()
{
Application.Run( new CreditInquiryForm() );
}
Outline
CreditInquiry.cs
// Visual Studio .NET generated code
// invoked when user clicks Open File button
private void openButton_Click(
object sender, System.EventArgs e )
{
// create dialog box enabling user to open file
OpenFileDialog fileChooser = new OpenFileDialog();
DialogResult result = fileChooser.ShowDialog();
// exit event handler if user clicked Cancel
if ( result == DialogResult.Cancel )
return;
// get name from user
fileName = fileChooser.FileName;
// show error if user specified invalid file
if ( fileName == "" || fileName == null )
MessageBox.Show( "Invalid File Name", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
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else
{
// enable all GUI buttons, except for Open file button
openButton.Enabled = false;
creditButton.Enabled = true;
debitButton.Enabled = true;
zeroButton.Enabled = true;
}
Outline
CreditInquiry.cs
} // end method openButton_Click
// invoked when user clicks credit balances,
// debit balances or zero balances button
private void get_Click( object sender, System.EventArgs e )
{
// convert sender explicitly to object of type button
Button senderButton = ( Button )sender;
// get text from clicked Button, which stores account type
string accountType = senderButton.Text;
// read and display file information
try
{
// close file from previous operation
if ( input != null )
input.Close();
// create FileStream to obtain read access to file
input = new FileStream( fileName, FileMode.Open,
FileAccess.Read );
displayTextBox.Text = "The accounts are:\r\n";
 2002 Prentice Hall.
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// traverse file until end of file
while ( true )
{
// get next Record available in file
Record record = ( Record )reader.Deserialize( input );
Outline
CreditInquiry.cs
// store record's last field in balance
Double balance = record.Balance;
// determine whether to display balance
if ( ShouldDisplay( balance, accountType ) )
{
// display record
string output = record.Account + "\t" +
record.FirstName + "\t" + record.LastName +
new string( ' ', 6 ) + "\t";
// display balance with correct monetary format
output += String.Format(
"{0:F}", balance ) + "\r\n";
// copy output to screen
displayTextBox.Text += output;
}
}
}
// handle exception when file cannot be closed
catch( IOException )
{
MessageBox.Show( "Cannot Close File", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
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// handle exception when no more records
catch( SerializationException )
{
// close FileStream if no Records in file
input.Close();
}
Outline
CreditInquiry.cs
} // end method get_Click
// determine whether to display given record
private bool ShouldDisplay( double balance, string accountType )
{
if ( balance > 0 )
{
// display credit balances
if ( accountType == "Credit Balances" )
return true;
}
else if ( balance < 0 )
{
// display debit balances
if ( accountType == "Debit Balances" )
return true;
}
else // balance == 0
{
// display zero balances
if ( accountType == "Zero Balances" )
return true;
}
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return false;
Outline
} // end method ShouldDisplay
// invoked when user clicks Done button
private void doneButton_Click(
object sender, System.EventArgs e )
{
// determine whether file exists
if ( input != null )
{
// close file
try
{
input.Close();
}
CreditInquiry.cs
// handle exception if FileStream does not exist
catch( IOException )
{
// notify user of error closing file
MessageBox.Show( "Cannot close file", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
Application.Exit();
} // end method doneButton_Click
} // end class CreditInquiryForm
 2002 Prentice Hall.
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50
Outline
CreditInquiry.cs
Program Output
 2002 Prentice Hall.
All rights reserved.
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Outline
CreditInquiry.cs
Program Output
 2002 Prentice Hall.
All rights reserved.
52
17.7 Random-Access Files
0
100
200
300
400
500
byte offsets
100
bytes
100
bytes
100
bytes
100
bytes
100
bytes
Fig. 17.13 Random-access file with fixed-length records.
 2002 Prentice Hall. All rights reserved.
100
bytes
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// Fig. 17.14: RandomAccessRecord.cs
// Data-record class for random-access applications.
using System;
public class RandomAccessRecord
{
// length of firstName and lastName
private const int CHAR_ARRAY_LENGTH = 15;
Outline
RandomAccessReco
rd.cs
private const int SIZE_OF_CHAR = 2;
private const int SIZE_OF_INT32 = 4;
private const int SIZE_OF_DOUBLE = 8;
// length of record
public const int SIZE = SIZE_OF_INT32 +
2 * ( SIZE_OF_CHAR * CHAR_ARRAY_LENGTH ) + SIZE_OF_DOUBLE;
// record data
private int account;
private char[] firstName = new char[ CHAR_ARRAY_LENGTH ];
private char[] lastName = new char[ CHAR_ARRAY_LENGTH ];
private double balance;
// default constructor sets members to default values
public RandomAccessRecord() : this( 0, "", "", 0.0 )
{
}
 2002 Prentice Hall.
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// overloaded counstructor sets members to parameter values
public RandomAccessRecord( int accountValue,
string firstNameValue, string lastNameValue,
double balanceValue )
{
Account = accountValue;
FirstName = firstNameValue;
LastName = lastNameValue;
Balance = balanceValue;
Outline
RandomAccessReco
rd.cs
} // end constructor
// property Account
public int Account
{
get
{
return account;
}
set
{
account = value;
}
} // end property Account
// property FirstName
public string FirstName
{
get
{
return new string( firstName );
}
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Outline
set
{
// determine length of string parameter
int stringSize = value.Length;
// firstName string representation
string firstNameString = value;
RandomAccessReco
rd.cs
// append spaces to string parameter if too short
if ( CHAR_ARRAY_LENGTH >= stringSize )
{
firstNameString = value +
new string( ' ', CHAR_ARRAY_LENGTH - stringSize );
}
else
{
// remove characters from string parameter if too long
firstNameString =
value.Substring( 0, CHAR_ARRAY_LENGTH );
}
// convert string parameter to char array
firstName = firstNameString.ToCharArray();
} // end set
} // end property FirstName
// property LastName
public string LastName
{
get
{
return new string( lastName );
}
 2002 Prentice Hall.
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Outline
set
{
// determine length of string parameter
int stringSize = value.Length;
RandomAccessReco
rd.cs
// lastName string representation
string lastNameString = value;
// append spaces to string parameter if too short
if ( CHAR_ARRAY_LENGTH >= stringSize )
{
lastNameString = value +
new string( ' ', CHAR_ARRAY_LENGTH - stringSize );
}
else
{
// remove characters from string parameter if too long
lastNameString =
value.Substring( 0, CHAR_ARRAY_LENGTH );
}
// convert string parameter to char array
lastName = lastNameString.ToCharArray();
} // end set
} // end property LastName
 2002 Prentice Hall.
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// property Balance
public double Balance
{
get
{
return balance;
}
Outline
RandomAccessReco
rd.cs
set
{
balance = value;
}
} // end property Balance
} // end class RandomAccessRecord
 2002 Prentice Hall.
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// Fig. 17.15: CreateRandomAccessFile.cs
// Creating a random file.
// C#
using
using
using
namespaces
System;
System.IO;
System.Windows.Forms;
Outline
CreateRandomAcce
ssFile.cs
// Deitel namespaces
using BankLibrary;
class CreateRandomAccessFile
{
// number of records to write to disk
private const int NUMBER_OF_RECORDS = 100;
[STAThread]
static void Main(string[] args)
{
// create random file, then save to disk
CreateRandomAccessFile file = new CreateRandomAccessFile();
file.SaveFile();
} // end method Main
// write records to disk
private void SaveFile()
{
// record for writing to disk
RandomAccessRecord blankRecord = new RandomAccessRecord();
// stream through which serializable data are written to file
FileStream fileOutput = null;
 2002 Prentice Hall.
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// stream for writing bytes to file
BinaryWriter binaryOutput = null;
// create dialog box enabling user to save file
SaveFileDialog fileChooser = new SaveFileDialog();
DialogResult result = fileChooser.ShowDialog();
Outline
CreateRandomAcce
ssFile.cs
// get file name from user
string fileName = fileChooser.FileName;
// exit event handler if user clicked Cancel
if ( result == DialogResult.Cancel )
return;
// show error if user specified invalid file
if ( fileName == "" || fileName == null )
MessageBox.Show("Invalid File Name", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error);
else
{
// write records to file
try
{
// create FileStream to hold records
fileOutput = new FileStream( fileName,
FileMode.Create, FileAccess.Write );
// set length of file
fileOutput.SetLength( RandomAccessRecord.SIZE *
NUMBER_OF_RECORDS );
// create object for writing bytes to file
binaryOutput = new BinaryWriter( fileOutput );
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// write empty records to file
for ( int i = 0; i < NUMBER_OF_RECORDS; i++ )
{
// set file position pointer in file
fileOutput.Position = i * RandomAccessRecord.SIZE;
Outline
CreateRandomAcce
ssFile.cs
// write blank record to file
binaryOutput.Write( blankRecord.Account );
binaryOutput.Write( blankRecord.FirstName );
binaryOutput.Write( blankRecord.LastName );
binaryOutput.Write( blankRecord.Balance );
}
// notify user of success
MessageBox.Show("File Created", "Success",
MessageBoxButtons.OK, MessageBoxIcon.Information);
}
// handle exception if error occurs during writing
catch( IOException )
{
// notify user of error
MessageBox.Show( "Cannot write to file", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
}
 2002 Prentice Hall.
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// close FileStream
if ( fileOutput == null )
fileOutput.Close();
// close BinaryWriter
if ( binaryOutput == null )
binaryOutput.Close();
Outline
CreateRandomAcce
ssFile.cs
} // end method SaveFile
} // end class CreateRandomAccessFile
Program Output
 2002 Prentice Hall.
All rights reserved.
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// Fig 17.16: WriteRandomAccessFile.cs
// Write data to a random-access file.
// C#
using
using
using
using
using
using
using
namespaces
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
System.IO;
Outline
WriteRandomAcces
sFile.cs
// Deitel namespaces
using BankLibrary;
public class WriteRandomAccessFileForm : BankUIForm
{
private System.Windows.Forms.Button openButton;
private System.Windows.Forms.Button enterButton;
private System.ComponentModel.Container components = null;
// number of RandomAccessRecords to write to disk
private const int NUMBER_OF_RECORDS = 100;
// stream through which data are written to file
private FileStream fileOutput;
// stream for writing bytes to file
private BinaryWriter binaryOutput;
 2002 Prentice Hall.
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[STAThread]
static void Main()
{
Application.Run( new WriteRandomAccessFileForm() );
}
Outline
WriteRandomAcces
sFile.cs
// Visual Studio .NET generated code
// invoked when user clicks Open button
private void openButton_Click(
object sender, System.EventArgs e )
{
// create dialog box enabling user to open file
OpenFileDialog fileChooser = new OpenFileDialog();
DialogResult result = fileChooser.ShowDialog();
// get file name from user
string fileName = fileChooser.FileName;
// exit event handler if user clicked Cancel
if ( result == DialogResult.Cancel )
return;
// show error if user specified invalid file
if ( fileName == "" || fileName == null )
MessageBox.Show("Invalid File Name", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error);
else
{
// open file if file already exists
try
{
// create FileStream to hold records
fileOutput = new FileStream( fileName,
FileMode.Open, FileAccess.Write );
 2002 Prentice Hall.
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// create object for writing bytes to file
binaryOutput = new BinaryWriter( fileOutput );
// disable Open button and enable Enter button
openButton.Enabled = false;
enterButton.Enabled = true;
Outline
WriteRandomAcces
sFile.cs
}
// notify user if file does not exist
catch( IOException )
{
MessageBox.Show("File Does Not Exits", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
} // end method openButton_Click
// invoked when user clicks Enter button
private void enterButton_Click(
object sender, System.EventArgs e )
{
// TextBox values string array
string[] values = GetTextBoxValues();
// determine whether TextBox account field is empty
if ( values[ ( int )TextBoxIndices.ACCOUNT ] != "" )
{
// write record to file at appropriate position
try
{
// get account number value from TextBox
int accountNumber = Int32.Parse(
values[ ( int )TextBoxIndices.ACCOUNT ] );
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// determine whether accountNumber is valid
if ( accountNumber > 0 &&
accountNumber <= NUMBER_OF_RECORDS )
{
// move file position pointer
fileOutput.Seek( ( accountNumber - 1 ) *
RandomAccessRecord.SIZE, SeekOrigin.Begin );
Outline
WriteRandomAcces
sFile.cs
// write data to file
binaryOutput.Write( accountNumber );
binaryOutput.Write(
values[ ( int )TextBoxIndices.FIRST ] );
binaryOutput.Write(
values[ ( int )TextBoxIndices.LAST ] );
binaryOutput.Write( Double.Parse( values[
( int )TextBoxIndices.BALANCE ] ) );
}
else
{
// notify user if invalid account number
MessageBox.Show("Invalid Account Number", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
// handle number-format exception
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catch( FormatException )
{
// notify user if error occurs when formatting numbers
MessageBox.Show("Invalid Balance", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
Outline
WriteRandomAcces
sFile.cs
}
ClearTextBoxes(); // clear text box values
} // end method enterButton_Click
} // end class WriteRandomAccessFileForm
Program Output
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Outline
WriteRandomAcces
sFile.cs
Program Output
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Outline
WriteRandomAcces
sFile.cs
Program Output
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Outline
WriteRandomAcces
sFile.cs
Program Output
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// Fig 17.17: ReadRandomAccessFile.cs
// Reads and displays random-access file contents.
// C#
using
using
using
using
using
using
using
namespaces
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
System.IO;
Outline
ReadRandomAccess
File.cs
// Deitel namespaces
using BankLibrary;
public class ReadRandomAccessFileForm : BankUIForm
{
private System.Windows.Forms.Button openButton;
private System.Windows.Forms.Button nextButton;
private System.ComponentModel.Container components = null;
// stream through which data are read from file
private FileStream fileInput;
// stream for reading bytes from file
private BinaryReader binaryInput;
// index of current record to be displayed
private int currentRecordIndex;
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[STAThread]
static void Main()
{
Application.Run( new ReadRandomAccessFileForm() );
}
Outline
ReadRandomAccess
File.cs
// Visual Studio .NET generated code
// invoked when user clicks Open button
private void openButton_Click(
object sender, System.EventArgs e )
{
// create dialog box enabling user to open file
OpenFileDialog fileChooser = new OpenFileDialog();
DialogResult result = fileChooser.ShowDialog();
// get file name from user
string fileName = fileChooser.FileName;
// exit eventhandler if user clicked Cancel
if ( result == DialogResult.Cancel )
return;
// show error if user specified invalid file
if ( fileName == "" || fileName == null )
MessageBox.Show( "Invalid File Name", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
else
{
// create FileStream to obtain read access to file
fileInput = new FileStream( fileName,
FileMode.Open, FileAccess.Read );
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// use FileStream for BinaryWriter to read bytes from file
binaryInput = new BinaryReader( fileInput );
openButton.Enabled = false; // disable Open button
nextButton.Enabled = true; // enable Next button
Outline
ReadRandomAccess
File.cs
currentRecordIndex = 0;
ClearTextBoxes();
}
} // end method openButton_Click
// invoked when user clicks Next button
private void nextButton_Click(
object sender, System.EventArgs e )
{
// record to store file data
RandomAccessRecord record = new RandomAccessRecord();
// read record and store data in TextBoxes
try
{
string[] values; // for storing TextBox values
// get next record available in file
while( record.Account == 0 )
{
// set file position pointer to next record in file
fileInput.Seek(
currentRecordIndex * RandomAccessRecord.SIZE, 0 );
currentRecordIndex += 1;
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// read data from record
record.Account = binaryInput.ReadInt32();
record.FirstName = binaryInput.ReadString();
record.LastName = binaryInput.ReadString();
record.Balance = binaryInput.ReadDouble();
}
Outline
ReadRandomAccess
File.cs
// store record values in temporary string array
values = new string[] {
record.Account.ToString(),
record.FirstName,
record.LastName,
record.Balance.ToString() };
// copy string array values to TextBox values
SetTextBoxValues( values );
}
// handle exception when no records in file
catch( IOException )
{
// close streams if no records in file
fileInput.Close();
binaryInput.Close();
openButton.Enabled = true; // enable Open button
nextButton.Enabled = false; // disable Next button
ClearTextBoxes();
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// notify user if no records in file
MessageBox.Show("No more records in file", "",
MessageBoxButtons.OK, MessageBoxIcon.Information);
}
} // end method nextButton_Click
Outline
ReadRandomAccess
File.cs
} // end class ReadRandomAccessFileForm
Program Output
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Outline
ReadRandomAccess
File.cs
Program Output
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Outline
ReadRandomAccess
File.cs
Program Output
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Outline
ReadRandomAccess
File.cs
Program Output
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Outline
ReadRandomAccess
File.cs
Program Output
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// Fig. 17.18: Transaction.cs
// Handles record transactions.
// C#
using
using
using
namespaces
System;
System.IO;
System.Windows.Forms;
Outline
Transaction.cs
// Deitel namespaces
using BankLibrary;
public class Transaction
{
// number of records to write to disk
private const int NUMBER_OF_RECORDS = 100;
// stream through which data move to and from file
private FileStream file;
// stream for reading bytes from file
private BinaryReader binaryInput;
// stream for writing bytes to file
private BinaryWriter binaryOutput;
// create/open file containing empty records
public void OpenFile( string fileName )
{
// write empty records to file
try
{
// create FileStream from new file or existing file
file = new FileStream( fileName, FileMode.OpenOrCreate );
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// use FileStream for BinaryWriter to read bytes from file
binaryInput = new BinaryReader( file );
// use FileStream for BinaryWriter to write bytes to file
binaryOutput = new BinaryWriter( file );
Outline
Transaction.cs
// determine whether file has just been created
if ( file.Length == 0 )
{
// record to be written to file
RandomAccessRecord blankRecord =
new RandomAccessRecord();
// new record can hold NUMBER_OF_RECORDS records
file.SetLength( RandomAccessRecord.SIZE *
NUMBER_OF_RECORDS );
// write blank records to file
for ( int i = 0; i < NUMBER_OF_RECORDS; i++ )
{
// move file-position pointer to next position
file.Position = i * RandomAccessRecord.SIZE;
// write blank record to file
binaryOutput.Write( blankRecord.Account );
binaryOutput.Write( blankRecord.FirstName );
binaryOutput.Write( blankRecord.LastName );
binaryOutput.Write( blankRecord.Balance );
}
}
}
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// notify user of error during writing of blank records
catch( IOException )
{
MessageBox.Show("Cannot create file", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error);
}
Outline
Transaction.cs
} // end method OpenFile
// retrieve record depending on whether account is valid
public RandomAccessRecord GetRecord( string accountValue )
{
// store file data associated with account in record
try
{
// record to store file data
RandomAccessRecord record = new RandomAccessRecord();
// get value from TextBox's account field
int accountNumber = Int32.Parse( accountValue );
// if account is invalid, do not read data
if ( accountNumber < 1 ||
accountNumber > NUMBER_OF_RECORDS )
{
// set record's account field with account number
record.Account = accountNumber;
}
// get data from file if account is valid
else
{
// locate position in file where record exists
file.Seek( ( accountNumber - 1 ) *
RandomAccessRecord.SIZE, 0 );
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// read data from record
record.Account = binaryInput.ReadInt32();
record.FirstName = binaryInput.ReadString();
record.LastName = binaryInput.ReadString();
record.Balance = binaryInput.ReadDouble();
Outline
Transaction.cs
}
return record;
}
// notify user of error during reading
catch( IOException )
{
MessageBox.Show( "Cannot read file", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
return null;
} // end method GetRecord;
// add record to file at position determined by accountNumber
public bool AddRecord(
RandomAccessRecord record, int accountNumber )
{
// write record to file
try
{
// move file position pointer to appropriate position
file.Seek( ( accountNumber - 1 ) *
RandomAccessRecord.SIZE, 0 );
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// write data to file
binaryOutput.Write(record.Account);
binaryOutput.Write(record.FirstName);
binaryOutput.Write(record.LastName);
binaryOutput.Write(record.Balance);
Outline
Transaction.cs
}
// notify user if error occurs during writing
catch( IOException )
{
MessageBox.Show( "Error Writing To File", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
return false; // failure
}
return true; // success
} // end method AddRecord
} // end class Transaction
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// Fig. 17.19: TransactionProcessor.cs
// MDI parent for transaction-processor application.
using
using
using
using
using
using
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
Outline
TransactionProce
ssor.cs
public class TransactionProcessorForm
: System.Windows.Forms.Form
{
private System.ComponentModel.Container components = null;
private System.Windows.Forms.MdiClient MdiClient1;
// reference to StartDialog
private StartDialogForm startDialog;
// constructor
public TransactionProcessorForm()
{
// required for Windows Form Designer support
InitializeComponent();
startDialog = new StartDialogForm();
startDialog.MdiParent = this;
startDialog.Show();
}
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[STAThread]
static void Main()
{
Application.Run( new TransactionProcessorForm() );
}
Outline
TransactionProce
ssor.cs
// Visual Studio .NET generated code
} // end class TransactionProcessorForm
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//
//
//
//
Fig. 17.20: StartDialog.cs
Initial dialog box displayed to user. Provides buttons for
creating/opening file and for adding, updating and removing
records from file.
// C#
using
using
using
using
using
Outline
StartDialog.cs
namespaces
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
// Deitel namespaces
using BankLibrary;
public delegate void MyDelegate();
public class StartDialogForm : System.Windows.Forms.Form
{
private System.Windows.Forms.Button updateButton;
private System.Windows.Forms.Button newButton;
private System.Windows.Forms.Button deleteButton;
private System.Windows.Forms.Button openButton;
private System.ComponentModel.Container components = null;
// reference to dialog box for adding record
private NewDialogForm newDialog;
// reference to dialog box for updating record
private UpdateDialogForm updateDialog;
// reference to dialog box for removing record
private DeleteDialogForm deleteDialog;
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// reference to object that handles transactions
private Transaction transactionProxy;
// Visual Studio .NET generated code
Outline
StartDialog.cs
// invoked when user clicks New/Open File button
private void openButton_Click(
object sender, System.EventArgs e )
{
// create dialog box enabling user to create or open file
OpenFileDialog fileChooser = new OpenFileDialog();
DialogResult result;
string fileName;
// enable user to create file if file does not exist
fileChooser.Title = "Create File / Open File";
fileChooser.CheckFileExists = false;
// show dialog box to user
result = fileChooser.ShowDialog();
// exit event handler if user clicked Cancel
if ( result == DialogResult.Cancel )
return;
// get file name from user
fileName = fileChooser.FileName;
// show error if user specified invalid file
if ( fileName == "" || fileName == null )
MessageBox.Show( "Invalid File Name", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
// open or create file if user specified valid file
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else
{
// create Transaction with specified file
transactionProxy = new Transaction();
transactionProxy.OpenFile( fileName );
Outline
StartDialog.cs
// enable GUI buttons except for New/Open File button
newButton.Enabled = true;
updateButton.Enabled = true;
deleteButton.Enabled = true;
openButton.Enabled = false;
// instantiate dialog box for creating records
newDialog = new NewDialogForm( transactionProxy,
new MyDelegate( ShowStartDialog ) );
// instantiate dialog box for updating records
updateDialog = new UpdateDialogForm( transactionProxy,
new MyDelegate( ShowStartDialog ) );
// instantiate dialog box for removing records
deleteDialog = new DeleteDialogForm( transactionProxy,
new MyDelegate( ShowStartDialog ) );
// set StartDialog as MdiParent for dialog boxes
newDialog.MdiParent = this.MdiParent;
updateDialog.MdiParent = this.MdiParent;
deleteDialog.MdiParent = this.MdiParent;
}
} // end method openButton_Click
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// invoked when user clicks New Record button
private void newButton_Click(
object sender, System.EventArgs e )
{
Hide(); // hide StartDialog
newDialog.Show(); // show NewDialog
Outline
StartDialog.cs
} // end method newButton_Click
private void updateButton_Click(
object sender, System.EventArgs e )
{
Hide(); // hide StartDialog
updateDialog.Show(); // show UpdateDialog
} // end method updateButton_Click
private void deleteButton_Click(
object sender, System.EventArgs e )
{
Hide(); // hide StartDialog
deleteDialog.Show(); // show DeleteDialog
} // end method deleteButton_Click
protected void ShowStartDialog()
{
Show();
}
} // end class StartDialogForm
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90
Outline
StartDialog.cs
Program Output
 2002 Prentice Hall.
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// Fig. 17.22: UpdateDialog.cs
// Enables user to update records in file.
// C#
using
using
using
using
using
namespaces
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
Outline
UpdateDialog.cs
// Deitel namespaces
using BankLibrary;
public class UpdateDialogForm : BankUIForm
{
private System.Windows.Forms.Label transactionLabel;
private System.Windows.Forms.TextBox transactionTextBox;
private System.Windows.Forms.Button saveButton;
private System.Windows.Forms.Button cancelButton;
private System.ComponentModel.Container components = null;
// reference to object that handles transactions
private Transaction transactionProxy;
// delegate for method that displays previous window
private MyDelegate showPreviousWindow;
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// initialize components and set members to parameter values
public UpdateDialogForm(
Transaction transactionProxyValue,
MyDelegate delegateValue )
{
InitializeComponent();
showPreviousWindow = delegateValue;
Outline
UpdateDialog.cs
// instantiate object that handles transactions
transactionProxy = transactionProxyValue;
}
// Visual Studio .NET generated code
// invoked when user enters text in account TextBox
private void accountTextBox_KeyDown(
object sender, System.Windows.Forms.KeyEventArgs e )
{
// determine whether user pressed Enter key
if ( e.KeyCode == Keys.Enter )
{
// retrieve record associated with account from file
RandomAccessRecord record =
transactionProxy.GetRecord( GetTextBoxValues()
[ ( int )TextBoxIndices.ACCOUNT ] );
// return if record does not exist
if ( record == null )
return;
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// determine whether record is empty
if ( record.Account != 0 )
{
// store record values in string array
string[] values = {
record.Account.ToString(),
record.FirstName.ToString(),
record.LastName.ToString(),
record.Balance.ToString() };
Outline
UpdateDialog.cs
// copy string array value to TextBox values
SetTextBoxValues( values );
transactionTextBox.Text = "[Charge or Payment]";
}
else
{
// notify user if record does not exist
MessageBox.Show(
"Record Does Not Exist", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
}
} // end method accountTextBox_KeyDown
// invoked when user enters text in transaction TextBox
private void transactionTextBox_KeyDown(
object sender, System.Windows.Forms.KeyEventArgs e )
{
// determine whether user pressed Enter key
if ( e.KeyCode == Keys.Enter )
{
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// calculate balance using transaction TextBox value
try
{
// retrieve record associated with account from file
RandomAccessRecord record =
transactionProxy.GetRecord( GetTextBoxValues()
[ ( int )TextBoxIndices.ACCOUNT ] );
Outline
UpdateDialog.cs
// get transaction TextBox value
double transactionValue =
Double.Parse( transactionTextBox.Text );
// calculate new balance (old balance + transaction)
double newBalance =
record.Balance + transactionValue;
// store record values in string array
string[] values = {
record.Account.ToString(),
record.FirstName.ToString(),
record.LastName.ToString(),
newBalance.ToString() };
// copy string array value to TextBox values
SetTextBoxValues( values );
// clear transaction TextBox
transactionTextBox.Text = "";
}
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// notify user if error occurs in parameter mismatch
catch( FormatException )
{
MessageBox.Show(
"Invalid Transaction", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
Outline
UpdateDialog.cs
}
} // end method transactionTextBox_KeyDown
// invoked when user clicks Save button
private void saveButton_Click(
object sender, System.EventArgs e )
{
RandomAccessRecord record =
transactionProxy.GetRecord( GetTextBoxValues()
[ ( int )TextBoxIndices.ACCOUNT ] );
// if record exists, update in file
if ( record != null )
UpdateRecord( record );
Hide();
ClearTextBoxes();
showPreviousWindow();
} // end method saveButton_Click
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// invoked when user clicks Cancel button
private void cancelButton_Click(
object sender, System.EventArgs e )
{
Hide();
ClearTextBoxes();
showPreviousWindow();
Outline
UpdateDialog.cs
} // end method cancelButton_Click
// update record in file at position specified by accountNumber
public void UpdateRecord( RandomAccessRecord record )
{
// store TextBox values in record and write record to file
try
{
int accountNumber = record.Account;
string[] values = GetTextBoxValues();
// store values in record
record.Account = accountNumber;
record.FirstName =
values[ ( int )TextBoxIndices.FIRST ];
record.LastName =
values[ ( int )TextBoxIndices.LAST ];
record.Balance =
Double.Parse(
values[ ( int )TextBoxIndices.BALANCE ] );
// add record to file
if ( transactionProxy.AddRecord(
record, accountNumber ) == false )
return; // if error
}
 2002 Prentice Hall.
All rights reserved.
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// notify user if error occurs in parameter mismatch
catch( FormatException )
{
MessageBox.Show( "Invalid Balance", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
Outline
UpdateDialog.cs
return;
}
MessageBox.Show( "Record Updated", "Success",
MessageBoxButtons.OK,
MessageBoxIcon.Information );
} // end method UpdateRecord
} // end class UpdateDialogForm
Program Output
 2002 Prentice Hall.
All rights reserved.
98
Outline
UpdateDialog.cs
Program Output
 2002 Prentice Hall.
All rights reserved.
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// Fig. 17.21: NewDialog.cs
// Enables user to insert new record into file.
// C#
using
using
using
using
using
namespaces
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
Outline
NewDialog.cs
// Deitel namespaces
using BankLibrary;
public class NewDialogForm : BankUIForm
{
private System.Windows.Forms.Button saveButton;
private System.Windows.Forms.Button cancelButton;
private System.ComponentModel.Container components = null;
// reference to object that handles transactions
private Transaction transactionProxy;
// delegate for method that displays previous window
public MyDelegate showPreviousWindow;
// constructor
public NewDialogForm( Transaction transactionProxyValue,
MyDelegate delegateValue )
{
InitializeComponent();
showPreviousWindow = delegateValue;
 2002 Prentice Hall.
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// instantiate object that handles transactions
transactionProxy = transactionProxyValue;
Outline
}
// Visual Studio .NET generated code
NewDialog.cs
// invoked when user clicks Cancel button
private void cancelButton_Click(
object sender, System.EventArgs e )
{
Hide();
ClearTextBoxes();
showPreviousWindow();
} // end method cancelButton_Click
// invoked when user clicks Save As button
private void saveButton_Click(
object sender, System.EventArgs e )
{
RandomAccessRecord record =
transactionProxy.GetRecord( GetTextBoxValues()
[ ( int )TextBoxIndices.ACCOUNT ] );
// if record exists, add it to file
if ( record != null )
InsertRecord( record );
Hide();
ClearTextBoxes();
showPreviousWindow();
} // end method saveButton_Click
 2002 Prentice Hall.
All rights reserved.
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// insert record in file at position specified by accountNumber
private void InsertRecord( RandomAccessRecord record )
{
//store TextBox values in string array
string[] textBoxValues = GetTextBoxValues();
Outline
NewDialog.cs
// store TextBox account field
int accountNumber = Int32.Parse(
textBoxValues[ ( int )TextBoxIndices.ACCOUNT ] );
// notify user and return if record account is not empty
if ( record.Account != 0 )
{
MessageBox.Show(
"Record Already Exists or Invalid Number", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error);
return;
}
// store values in record
record.Account = accountNumber;
record.FirstName =
textBoxValues[ ( int )TextBoxIndices.FIRST];
record.LastName =
textBoxValues[ ( int )TextBoxIndices.LAST];
record.Balance = Double.Parse(
textBoxValues[ ( int )TextBoxIndices.BALANCE ] );
// add record to file
try
{
if ( transactionProxy.AddRecord(
record, accountNumber ) == false )
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return; // if error
Outline
}
// notify user if error occurs in parameter mismatch
catch( FormatException )
{
MessageBox.Show( "Invalid Balance", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
}
NewDialog.cs
MessageBox.Show( "Record Created", "Success",
MessageBoxButtons.OK, MessageBoxIcon.Information );
} // end method InsertRecord
} // end class NewDialogForm
Program Output
 2002 Prentice Hall.
All rights reserved.
103
Outline
NewDialog.cs
Program Output
 2002 Prentice Hall.
All rights reserved.
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// Fig. 17.23: DeleteDialog.cs
// Enables user to delete records in file.
// C#
using
using
using
using
using
namespaces
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
Outline
DeleteDialog.cs
// Deitel namespaces
using BankLibrary;
public class DeleteDialogForm : System.Windows.Forms.Form
{
private System.Windows.Forms.Label accountLabel;
private System.Windows.Forms.TextBox accountTextBox;
private System.Windows.Forms.Button deleteButton;
private System.Windows.Forms.Button cancelButton;
private System.ComponentModel.Container components = null;
// reference to object that handles transactions
private Transaction transactionProxy;
// delegate for method that displays previous window
private MyDelegate showPreviousWindow;
// initialize components and set members to parameter values
public DeleteDialogForm( Transaction transactionProxyValue,
MyDelegate delegateValue)
{
InitializeComponent();
showPreviousWindow = delegateValue;
 2002 Prentice Hall.
All rights reserved.
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// instantiate object that handles transactions
transactionProxy = transactionProxyValue;
}
Outline
DeleteDialog.cs
// Visual Studio .NET generated code
// invoked when user clicks Delete Record button
private void deleteButton_Click(
object sender, System.EventArgs e)
{
RandomAccessRecord record =
transactionProxy.GetRecord( accountTextBox.Text );
// if record exists, delete it in file
if ( record != null )
DeleteRecord( record );
this.Hide();
showPreviousWindow();
} // end method deleteButton_Click
// invoked when user clicks Cancel button
private void cancelButton_Click(
object sender, System.EventArgs e)
{
this.Hide();
showPreviousWindow();
} // end method cancelButton_Click
 2002 Prentice Hall.
All rights reserved.
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// delete record in file at position specified by accountNumber
public void DeleteRecord( RandomAccessRecord record )
{
int accountNumber = record.Account;
Outline
DeleteDialog.cs
// display error message if record does not exist
if ( record.Account == 0 )
{
MessageBox.Show( "Record Does Not Exist", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
accountTextBox.Clear();
return;
}
// create blank record
record = new RandomAccessRecord();
// write over file record with empty record
if ( transactionProxy.AddRecord(
record, accountNumber ) == true )
// notify user of successful deletion
MessageBox.Show( "Record Deleted", "Success",
MessageBoxButtons.OK, MessageBoxIcon.Information );
 2002 Prentice Hall.
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else
// notify user of failure
MessageBox.Show(
"Record could not be deleted", "Error",
MessageBoxButtons.OK, MessageBoxIcon.Error );
Outline
DeleteDialog.cs
accountTextBox.Clear();
} // end method DeleteRecord
} // end class DeleteDialogForm
Program Output
 2002 Prentice Hall.
All rights reserved.