C# tutorial

Enumeration (Enums)
Value and Reference Types
Constructor and this Keyword
static Keyword
Encapsulation Services
Inheritance
Inheritance II
Polymorphism
Interfaces
Delegates
System.Object
Events
Multi Threading I - Introduction and Simple Thread
Multi Threading II - ThreadStart/ParameterizedThreadStart,
Foreground/Background Threads
Multi Threading III - Concurrency, Synchronization
Networking I - PORT, IPv4/IPv6, TCP/UDP, URI
Networking II - WebRequest/WebResponse, WebClient

Introduction
C# is a multi-paradigm programming language encompassing imperative,
declarative, functional, generic, object-oriented, and component-oriented programming
disciplines.

It was developed by Microsoft within the .NET initiative and later approved as a
standard by Ecma (ECMA-334) and ISO (ISO/IEC 23270). C# is one of the
programming languages designed for the Common Language Infrastructure (CLI).

C# is intended to be a simple, modern, general-purpose, object-oriented programming
language. Its development team is led by Anders Hejlsberg. The most recent version
is C# 4.0, which was released on April 12, 2010.

What's new in C# 4.0

C# 4.0 is the latest version, which was released in April 11, 2010. Microsoft has
released the 4.0 runtime and development environment Visual Studio 2010. The major
focus of C# 4.0 is interoperability with partially or fully dynamically typed languages
and frameworks, such as the Dynamic Language Runtime and COM.

Your Ad Here

Here are new features:

Dynamic member lookup
A new pseudo-type dynamic is introduced into the C# type system. It is treated
as System.Object, but in addition, any member access (method call, field,
property, or indexer access, or a delegate invocation) or application of an
operator on a value of such type is permitted without any type checking, and its
resolution is postponed until run-time. This is known asDuck typing.

Covariant and contravariant generic type parameters
Generic interfaces and delegates can have their type parameters marked
as covariant or contravariant, using keywords out and in, respectively.
These declarations are then respected for type conversions, both implicit and
explicit, and both compile-time and run-time.

Optional ref Keyword when using COM
The ref keyword for callers of methods is now optional when calling into methods
supplied by COM interfaces.

Optional parameters and named arguments
C# 4.0 introduces optional parameters with default values as seen in Visual Basic
and C++.

Indexed properties
Indexed properties (and default properties) of COM objects are now recognized,
but C# objects still do not support them.

Visual Studio Command Prompt

You can invoke the C# compiler by typing the name of its executable file, csc.exe on
the command line. If you use the Visual Studio Command Prompt (available as a
shortcut on the start menu under Visual Studio Tools), all the necessary environment
variables are set for you. Otherwise, you must adjust your path in order to
enable csc.exe to be invoked from any subdirectory on your computer. If you do not
use the Visual Studio Command Prompt, you must
run vsvars32.bat under C:Program Files (x86)Microsoft Visual Studio
10.0Common7Tools to set the appropriate environment variables to support
command line builds.

Let's start with Visual Studio 2010:
Start -> Programs -> Visual Studio 2010 -> Visual Studio Tools.

Then, type in

csc -?

We get:

If we want to make it work on other command prompt, we should set the new path.
For my system the paths are:

C:WindowsMicrosoft.NETFramework64v4.0.30319
C:Program Files (x86)Microsoft SDKsWindowsv7.0ABin
C:Program Files (x86)Microsoft Visual Studio 10.0SDKv3.5Bin

Once you have updated your Path variable, close all dialog boxes and any currently
opened Console windows to commit the settings. You should now be able to execute
csc.exe and other .NET tools from any Command prompt. To test, enter the following
commands:

csc -?
ildasm -?

We can check it's working if we see the same output as the one running from the Visual
Studio Prompt.

Simple Command Line C#

Option Description

This option is used to specify the name of the assembly to be created. By
/out
default, the assembly name is the same as the name of the initial input *.cs file.

This option is used to specify the name of the assembly to be created. By
/target:exe
default, the assembly name is the same as the name of the initial input *.cs file.

/target:library This option builds a single-file *.dll assembly

/target:module This option builds a module. Modules are elements of multifile assemblies.

Although we are free to build graphical user interface-based applications using
/target:winexe
the target:exe. Modules are elements of multifile assemblies.

Compiles File.cs producing File.exe

csc /target:exeFile.cs

Compiles File.cs using abbreviation producing File.exe

csc /t:exeFile.cs

Compiles File.cs producing File.exe because /t:exe is the default output.

cscFile.cs

Compiles File.cs producing File.dll

csc /target:libraryFile.cs

Compiles File.cs and creates MyCSharp.exe:

csc /out:MyCSharp.exe File.cs

Compiles all the C# files in the current directory, with optimizations on and
defines the DEBUG symbol. The output is File2.exe

csc /define:DEBUG /optimize /out:File2.exe *.cs

Compiles all the C# files in the current directory producing a debug version of
File2.dll. No logo and no warnings are displayed

csc /target:library /out:File2.dll /warn:0 /nologo /debug *.cs

Compiles all the C# files in the current directory to Something.useful (a DLL):

csc /target:library /out:Something.useful *.cs

C# Compiler vs. C++ Compiler

There are no object (.obj) files created as a result of invoking the C# compiler; output
files are created directly. As a result of this, the C# compiler does Not need a linker

My First C# Program

Here is our first C# code:

// Program.cs
using System;
usingSystem.Collections.Generic;
usingSystem.Linq;
usingSystem.Text;

namespaceMyFirstCSharpCode
{
class Program
{
static void Main(string[] args)
{
}
}
}

A C# program consists of one or more type declarations. C# requires that all program
be contained within a type (class, interface, structure, enumeration, delegate etc.)
definition. In other words, all data members and methods must be contained within a
type definition. In the above example, only the class type is declared.

The code is created as a new Console Application project
named MyFirstCSharpCode.

The program uses two namespaces. It creates a new namespace
called MyFirstCSharpCode, and uses a predefined namespace called System.

The method Main() is a member of class MyFirstCSharpCode and it's a special
function used by the compiler as the starting point of the program. By default, Visual
Studio names the class defining Main(). Here, it's the Program. So, the file name
isProgram.cs. However, we are free to change this if we so choose.

The class that defines the Main() method is termed the application object (which
can be useful when performing unit tests), we must inform the compiler
which Main() method should be used as the entry point via the /main option of the
command-line compiler.

Note that the signature of Main() is adorned with the static keyword. Static members
are scoped to the class level rather than the object level and can thus be invoked
without the need to first create a new class instance.

In addition to the static keyword, this Main() method has a single parameter, which is
an array of strings:

string[] args

To compile the program, we can use Visual Studio or the command-line compiler. To
use the command-line compiler, use the following command:

cscProgram.cs

In this command, csc is the name of the command-line compiler and Program.cs is
the name of the source file.

Let's make the code more interesting:

// Program2.cs
using System;
usingSystem.Linq;
usingSystem.Text;

{
class Program2
{
static void Main(string[] args)
{
Console.WriteLine("My first C# code");
Console.WriteLine("Hello World");
Console.WriteLine();
Console.ReadLine();
}
}
}

In the new code, we make use of the Console class, which is defined within
the System namespace. Among its set of members is the static WriteLine() which
pumps a text string and carriage return to the standard output. We also make a call
toConsole.ReadLine() to ensure the command prompt launched by the Visual Studio
2010 IDE remains visible during a debugging session until we press the Enter key.

Note that we have several methods for our Main():

static int Main(string[] args)
static void Main()
static int Main()

Error Code

The ability to return an int from Main() keeps C# consistent with other C-based
languages. By convention, returning the value 0indicates the program has terminated
successfully, while another value such as -1 represents an error condition.

On the Windows OS, an application's return value is stored within a system
environment variable named %ERRORLEVEL%. If we were to create an application
that programmatically launches another executable, we can obtain the value
of%ERRORLEVEL% using the
static System.Diagnostics.Process.ExitCode property.

Given that an application's return value is passed to the system at the time the
application terminates, it is obviously not possible for an application to obtain and
display its final error code while running. However, to illustrate how to view this error
level upon program termination, begin by updating the Main() method:

// Program3.cs
using System;
usingSystem.Linq;
usingSystem.Text;

{
class Program3
{
staticint Main(string[] args)
{
Console.WriteLine("Hello World!");
Console.ReadLine();
return -1;
}
}
}

Let's capture Main()'s return value with the help of a batch file. Using the Windows
Explorer, put MyFirstCSharpCode.bat intoC:DocumentsVisual Studio
2010ProjectsMyFirstCSharpCode folder. The file looks like this:

@echo off

rem A batch file for MyFirstCSharpCode.exe
rem which captures the app's return value.

MyFirstCSharpCode
@if "%ERROELEVEL%" == "0" goto success

:fail
echo This application has failed!
echo return value = %ERRORLEVEL%
goto end
:success
echo This application has succeeded!
echo return value = %ERRORLEVEL%
goto end
:end
echo Done.

Let's open a command prompt and navigate to the folder containing our executable and
the new batch file. Execute the batch file by typing in the
name MyFirstCSharpCode.bat and pressing the Enter key. We'll get:

My first C# code
Hello World!

Testing Error
This application has failed!
return value = -1
Done..

However, a vast majority of our C# application will use void as the return value
from Main(), which implicitly returns the error code of zero. We may not the batch file
at all.

Command-Line Arguments

Let's look at the incoming array of string data. Now we want to update our application
to process any possible command-line parameters using a C# for loop.

// Program4.cs
using System;
usingSystem.Linq;
usingSystem.Text;

{
class Program4
{
{

for(inti = 0; i<args.Length; i++)
Console.WriteLine("Arg: {0}", args[i]);
Console.ReadLine();
return -1;
}
}
}

Here, we are checking to see whether the array of strings contains the number of
items using the Length property ofSystem.Array.

C:>cd CSharp

C:CSharp>csc Program4.cs
Microsoft (R) Visual C# 2010 Compiler version 4.0.30319.1
Copyright (C) Microsoft Corporation. All rights reserved.

C:CSharp>Program4 argAargBargC
My first C# code
Hello World!

Arg: argA
Arg: argB
Arg: argC

C:CSharp>

As we loop over each item in the array, its value is printed to the console window.

We can use an alternative to the standard for loop. We may iterate over an
incoming string array using the C# foreachkeyword:

foreach(string a in args)
Console.WriteLine("Arg: {0}", a);

We are also able to access command-line argument using the
static GetCommandLineArgs() method of theSystem.Environment type. The
return value of this method is an array of strings. The first index identifies the name of
the application itself, while the remaining elements in the array contain the individual
command-line arguments.

// Program5.cs
using System;
usingSystem.Linq;

usingSystem.Text;

{
class Program5
{
{
string[] arguments = Environment.GetCommandLineArgs();
foreach(string arg in arguments)
Console.WriteLine("Arg: {0}", arg);
Console.ReadLine();
return -1;
}
}
}

Output is

C:CSharp>csc Program5.cs
Microsoft (R) Visual C# 2010 Compiler version 4.0.30319.1
Copyright (C) Microsoft Corporation. All rights reserved.

C:CSharp>Program5 argAargBargC
My first C# code
Hello World!

Arg: Program5
Arg: argA
Arg: argB
Arg: argC

C:CSharp>

Command-Line Arguments with Visual Studio 2010

While in the real world, the user supplies the command-line arguments, we may want
to specify command-line argument during the development cycle.

To specify the arguments with Visual Studio 2010, double-click the Properties icon from
Solution Explorer.

Then, select the Debug tab on the left side. After that we can specify values using the
Command line arguments text box.

List of C# Tutorials

.NET Framework
Introduction - My First C# Code
System Members and Data
Modifiers
Array
Enumeration (Enums)
Value and Reference Types
Constructor and this Keyword
static Keyword
Encapsulation Services
Inheritance
Inheritance II
Polymorphism
Interfaces
Delegates
System.Object
Events

Multi Threading I - Introduction and Simple Thread
Multi Threading II - ThreadStart/ParameterizedThreadStart,
Foreground/Background Threads
Multi Threading III - Concurrency, Synchronization
Networking I - PORT, IPv4/IPv6, TCP/UDP, URI
Networking II - WebRequest/WebResponse, WebClient

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