Transcript ASP.NET Best Practices - Missouri State University

ASP.NET Best Practices
Dawit Wubshet
Park University
StringBuilder
The StringBuilder class starts with a default
initial capacity of 16.
Strings less than the initial capacity are stored in
the StringBuilder object.
The initial capacity of the buffer can be set by
using the following overloaded constructor:
public StringBuilder (int capacity);
For example: StringBuilder sb = new
StringBuilder(2000);
StringBuilder
Use StringBuilder when you need to concatenate
strings multiple times.
// using String and '+' to append
String str = "Some Text";
for ( ... loop several times to build the string ...) {
str = str + " additional text ";
}
// using String and .Append method to append
StringBuilder strBuilder = new StringBuilder("Some Text
");
for ( ... loop several times to build the string ...) {
strBuilder.Append(" additional text ");
}
StringBuilder
Use StringBuilder when the number of
appends is unknown.
Code sample:
for (int i=0; i< Results.Count; i++)
{
StringBuilder.Append (Results[i]);
}
StringBuilder
Treat StringBuilder as an accumulator or reusable
buffer.
Avoids the allocations of temporary strings during
multiple append iterations. Some of the scenarios where
this helps are as follows:
Concatenating strings: You should always prefer the
following approach to string concatenation when using
StringBuilder.
StringBuilder sb;
sb.Append(str1);
sb.Append(str2);
Use the preceding code rather than the following.
sb.Append(str1+str2);
StringBuilder
Concatenating strings from various functions.
Example:
StringBuilder sb;
sb.Append(f1(...));
sb.Append(f2(...));
sb.Append(f3(...));
The preceding code snippet results in temporary string
allocations for the return values by the functions f1 (...),
f2 (...), f3 (...).
This can be avoided by following this approach:
void f1( sb,...);
void f2( sb,...);
void f3( sb,...);
Round Trips to the Server
Round trips to a server needs to be reduced by:
Prevalidating data on the client-side. Use
validation controls to implement client-side
validation of user input. Example:
<asp:requiredfieldvalidator id="rqrdUsername"
runat="server" Display=“Dynamic"
ControlToValidate="txtUsername">
Required.</asp:requiredfieldvalidator>
Using AJAX, Javascript.
View State
View state is turned on in ASP.NET by default.
Disable view state if you do not need it. For
example, you might not need view state because
your page is output-only or because you
explicitly reload data for each request. You do
not need view state when the following
conditions are true:
● Your page does not post back.
● You do not handle server control events.
● You repopulate controls with every page
refresh.
View State
Ways to disable view state at various levels:
To disable view state for all applications on a Web
server, configure the <pages> element in the
Machine.config file as follows:
<pages enableViewState="false" />
To disable view state for a single control on a page, set
the EnableViewState property of the control to false:
//Run time
yourControl.EnableViewState = false;
//Design time
<asp:datagrid EnableViewState="false" runat="server" />
To disable view state for a single page, use the @ Page
directive as follows:
<%@ Page EnableViewState="false" %>
Redirecting Between Pages
Where possible, use the Server.Transfer
method instead of the Response.Redirect
method.
If you need authentication and authorization
checks during redirection, use
Response.Redirect.
When you use Response.Redirect, ensure you
use the overloaded method that accepts a
Boolean second parameter:
Response.Redirect(“Adminlogin.aspx”, false);
To transfer to pages in other applications, you
must use Response.Redirect.
Resource Acquisition &
Disposing
Open critical, limited, and shared resources just before
you need them, and release them as soon as you can.
Critical, limited, and shared resources include resources
such as database connections, network connections,
and transactions. For example:
conn.Open();
SqlCommand comm = new
SqlCommand(“park_sp_GetAMember”, conn);
Instead of:
conn.Open();
restructureInput();
…
SqlCommand comm = new
SqlCommand(“park_sp_GetAMember”, conn);
Resource Acquisition &
Disposing
Use Try/Finally on disposable resources. To guarantee
resources are cleaned up when an exception occurs,
use a try/finally block. Close the resources in the finally
clause:
try
{
conn.Open();
...
}
finally
{
if (null != conn)
conn.close;
}
Pages
Trim your page size.
Enable buffering.
Ensure debug is set to false.
Optimize expensive loops.
Pages
To trim your page size, you can do one or all of the following:
● Use script includes for any static scripts in your page to enable the
client to cache these scripts for subsequent requests:<script
language=jscript src="scripts\myscript.js">
● Remove characters such as tabs and spaces that create white
space before you send a response to the client.
// with white space
<table>
<tr>
<td>hello</td>
<td>world</td>
</tr>
</table>
The following sample table does not contain white spaces.
// without white space
<table>
<tr><td>hello</td><td>world</td></tr>
</table>
Pages
If buffering is turned off, you can enable
buffering by using the following methods:
● Enable buffering programmatically in a page.
Response.BufferOutput = true;
● Enable buffering at the page level by using the
@Page directive: <%@ Page Buffer = "true" %>
● Enable buffering at the application or computer
level by using the <pages> element in the
Web.config or Machine.config file: <pages
buffer="true" ...>
Pages
Ensure Debug is set to false: <compilation debug="false"
... />
To set debug to false at the page level: <%@ Page
debug="false" ... %>
When debug is set to true, the following occurs:
● Pages are not batch compiled.
● Pages do not time out. When a problem occurs, such
as a problem with a Web service call, the Web server
may start to queue requests and stop responding.
● Additional files are generated in the Temporary
ASP.NET Files folder.
● The System.Diagnostics.DebuggableAttribute
attribute is added to generated code. This causes the
CLR to track extra information about generated code,
and it also disables certain optimizations.
Iterating and Looping
Avoid repetitive field or property access
If you use data that is static for the duration of the loop, obtain it
before the loop instead of repeatedly accessing a field or property.
The following code shows a collection of orders being processed for
a single customer.
for ( int item = 0; item < Customer.Orders.Count ; item++ ){
CalculateTax ( Customer.State, Customer.Zip,
Customer.Orders[item] );
}
Instead:
string state = Customer.State;
string zip = Customer.Zip;
int count = Customers.Orders.Count;
for ( int item = 0; item < count ; item++ )
{
CalculateTax (state, zip, Customer.Orders[item] );
}
Iterating and Looping
Optimize or avoid expensive operations within loops
Identify operations in your loop code that can be optimized. Look for
code that causes boxing or allocations as a side effect. The
following code causes side effect strings to be created for each pass
through the loop.
String str;
Array arrOfStrings = GetStrings();
for(int i=0; i<10; i++)
{
str+= arrOfStrings[i];
}
To avoid extra string allocations:
StringBuilder sb = new StringBuilder();
Array arrOfStrings = GetStrings();
for(int i=0; i<10; i++)
{
sb.Append(arrOfStrings.GetValue(i));
}
Iterating and Looping
Consider replacing recursion with looping since each recursive call
adds data to the stack. Example:
Array arr = GetArrayOfStrings();
int index = arr.Length-1;
String finalStr= RecurStr(index);
string RecurStr(int ind){
if (ind <= 0)
return "";
else
return (arr.GetValue(ind)+RecurStr(ind-1));
}
Rewritten:
string ConcString (Array array){
StringBuilder sb = new StringBuilder();
for (int i= array.Length; i>0; i--){
sb.Append(array.GetValue(i));
}
return sb;
Iterating and Looping
Use for instead of foreach in performance-critical code
paths since .NET uses an enumerator to provide
enhanced navigation through arrays and collections.
Instead of:
for (int i=0; i<yourControl.Items.Count; i++){
…
}
Use:
foreach (Control ctrl in yourControl)
{
…
}
Additional Resources
Microsoft Application Blocks:
http://msdn2.microsoft.com/enus/library/ms954836.aspx
FxCop:
http://www.gotdotnet.com/team/fxcop/
ASP.Net Analyzer:
http://msdn2.microsoft.com/enus/vstudio/aa718345.aspx
Questions
???