Transcript .NET - East Tennessee State University

.NET
What Is It And Why Use It?
7/17/2015
.NET - What and Why
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Software from Components
• In the industrial revolution, engineers
learned to build things in a consistent,
predictable, and repeatable way
• They learned to use assembly lines to
assemble items from components
• Any component of a given type and
specification is interchangeable with
another of the same type
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Why not build software the same way?
• Multiple languages and incompatibilities
• Basic, C, C++, COBOL, Visual Basic, C#,
Java, Fortran, Perl, Python, Eiffel, Delphi,
SQL, Pascal, PL/I, APL, assembly, Scheme,
Smalltalk, Prolog, Lisp, RPG, Ada, Ruby, …
• Cannot just take a piece of code from a Lisp
program, for example, and plug it into a
COBOL program and have it work
• Usually, cannot even call an Ada function
from a Python program without special
efforts, for example
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Why not build software the same way?
• Different Data Types
• Many different data types
• Not implemented the same way in all
languages (consider the many ways strings
are implemented)
• Implementations vary in size
• Character type may be 1 byte (ASCII or EBCDIC)
or 2 bytes (or even 4) for Unicode
• Integers may be 16 bits, 32 bits, 64 bits, etc.
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Why not build software the same way?
• Different conventions
• Argument passing may be left-to-right or
right-to-left
• Arguments in various languages may be
passed using a stack, others use registers,
pointers, or some other means; not
consistent among languages
• Name collisions
• Same word may be used differently in
different languages – a function name in one
may be a keyword in another
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Why not build software the same way?
• Different platforms and architectures
• Addresses and data: 16-bit, 32-bit, 64-bit,…
• Big-endian vs. little-endian (the number 01234567 is stored
with the 01 at the lowest address in big-endian and at the
highest address in little-endian: 01234567 vs. 67452301)
• IBM's 370 mainframes, most RISC-based computers, and
Motorola microprocessors use the big-endian approach. TCP/IP
also uses the big-endian approach (and thus big-endian is
sometimes called network order).
• Intel processors (CPUs) and DEC Alphas and at least some
programs that run on them are little-endian.
• Different instruction sets
• Differences in register architecture
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Why not build software the same way?
• Different operating systems even on the
same hardware
• Almost all user software depends on and
uses services (I/O, memory management,
processor management, etc.) provided by the
OS and its subsystems
• Different OS’s have different ways of
implementing the services, different API’s,
different conventions, different levels of
support for various activities
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Why not build software the same way?
• Different Human Languages; Different Cultures
• English, French, Japanese, Chinese, German, …
• Punctuation: In the US, 1.23 represents 1 and 23
hundredths, while in many European cultures, the
same value would be represented as 1,23
• Temperature: Fahrenheit vs. Celsius; in US 30
degrees is cold while in Canada 30 degrees is hot
• Currency: US Dollars vs. Canadian Dollars, Euros,
Yen, Rubles, ...
• Dates: 03/04/2014 is March 4, 2014 in the US but it
is April 3, 2014 in much of Europe
• English vs. Metric measures: Inches, miles, gallons,
pounds vs. centimeters, kilometers, liters, and
kilograms
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COM, CORBA, Enterprise Java Beans
• Various companies and groups of
companies came up with approaches that
could be used to standardize things and
allow components to work together
• Problems:
• All approaches were proprietary
• Approaches incompatible with each other
• Not based on open standards
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.NET
• Based on a open standard developed by
Microsoft, Intel, IBM, and others
• Approved as a standard by ECMA
• Approved as a standard by ISO
• Standards cover CTS, CLS, C#, and other items
• Designed to be language independent
• Platform neutral
• Open to development by anyone
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Common Type System (CTS)
• All .NET languages support common types –
though not necessarily using the same name
• System.Int32 is called int in C++ and C#, and
Integer in VB, but they are same type and can be
passed back and forth as arguments
• System.Single is called Single in VB and float in
C++ and C#, but all are the same type and are
interchangeable in the .NET languages
• Languages are free to add types, but added types
may not be compatible with other CTS languages
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Common Language Specification (CLS)
• All .NET languages must support a minimal
subset of .NET features and classes
• For example, all must support the CTS, the same
.NET class libraries, and so forth
• The CLS is a set of rules to which a language
compiler must adhere in order to create .NET
applications that run in the CLR
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Common Language Runtime (CLR)
•
All .NET compilers emit platform-neutral Intermediate Language (IL) object
code rather than native machine language code
•
Output of a project is called an Assembly
•
May be either a .EXE or a .DLL
•
Only the CLR needs to know what platform it is running on
•
CLR contains a JIT compiler that turns IL into native machine language
optimized for its target machine
•
Very fast and efficient
•
Done only once and only as needed
•
CLR also handles garbage-collection, exception handling, cross-language
debugging, and distributed debugging, and other common features
•
Includes runtime support for thousands of .NET classes
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IL Example
.method public hidebysig static void Main() cil managed
{
.entrypoint
.custom instance void [mscorlib]System.STAThreadAttribute::.ctor() =
// Code size
14 (0xe)
.maxstack 8
IL_0000: nop
IL_0001: newobj instance void ManageDB.frmTblMgmt::.ctor()
IL_0006: call
void
[System.Windows.Forms]System.Windows.Forms.Application::Run
(class [System.Windows.Forms]System.Windows.Forms.Form)
IL_000b: nop
IL_000c: nop
IL_000d: ret
} // end of method frmTblMgmt::Main
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Runtime Compilation and Execution
default.aspx
Which language?
C# code
C# Compiler
JIT compiler
Visual Basic .NET code
VB.NET compiler
MSIL
CLR
Native
code
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Platform Neutral
• Because the IL code is not targeted at
any platform, it is portable between
systems
• A (.NET) .exe and a (.NET) .dll compiled
on a Windows system will run on an
Apple or an IBM mainframe IF it has its
own CLR to convert the IL code to native
code targeted to the machine on which it
is to run and to provide the runtime
support for the .NET classes
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Language Interoperability
• The standards that are part of .NET insure that
a control developed in VB.NET can be used in
a C# program
• A method written in a business-tier class in
COBOL.NET can be invoked by a VB.NET
Windows Forms front end
• A .NET string in a Delphi.NET program
compiled using a Borland compiler on a
Windows computer can be passed to a C#
method written using a SSCLI compiler running
on an Apple OS-X platform
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.NET Implementations
• Implementations of .NET and its standard
technologies include
• Microsoft’s .NET Framework and Visual
Studio.NET
• The Shared Source Common Language Initiative
(SSCLI) that runs on BSD Unix and Apple OS-X
• Mono open source effort led by Novell and others
• More than 30 languages support .NET:
• Microsoft: VB.NET, C#, J#, managed C++, Cω,
Spec# , F#, JavaScript, Typescript
• Python, Perl, Cobol, Delphi, Pascal, Eiffel, and
many others by non-Microsoft vendors
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Much of .NET to be Open Sourced
Announced 4/3/2014
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The .NET Framework Components
Visual
Basic
C++
C#
Perl
Python
…
XML Web Services
User Interface
ASP.NET
Web Apps and
Services
ADO.NET and XML
Base Class
Library
.NET Framework Class Library
Message
Queuing
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Web Server
Common Language Runtime
JIT, GC, Exceptions,
Debugging, etc.
Base OS API
Database
support
COM+
(Transactions, Partitions,
Object Pooling)
IIS
WMI
Win32
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Thus, …
• Solutions/Applications can be developed in any
.NET language or languages (by project) that
fully supports the features used by the
application and that adheres to the standards
• Different parts of an application (solution) can
be developed in different languages
• Visual Studio compiles a project with a single
language compiler, thus source code within a
project must be in same language, but it can
use components such as class libraries written
and compiled in other languages
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