C # extension method [learning]

C # can be defined Extension Method , You can also Extension Method for the set .

Example:

Extension Method

Using System;
Using System. Collections. Generic;

Using MySpace; // Note: space for introducing extension methods

Namespace Con_1
{
Class Program
{
Static   Void Main ( String [] ARGs)
{
String Str =   " Mr. {0. " . ( " Xugang " );
Console. writeline ( " Hello! "   + Str );

//2 call the extension method of the Set
Str. showitems<Char>();
}
}
}

Namespace MySpace
{
// Extension methods must be defined in non-generic static classes.
Public   Static   Class Mymethods
{
// Note: The first parameter uses "this" to obtain the current object.
Public   Static   String With ( This   String _ Context, Params   String [] _ ARGs)
{
Return   String . Format (_ context, _ ARGs );
}

// 2. Perform expansion for the set
Public   Static   Void Showitems < T > ( This Ienumerable < T > _ Al)
{
Foreach (VAR item In _ Al)
{
Console. writeline (item );
}
}
}
}

Note:

1 C # Only extension methods are supported, and extended attributes and events are not supported;

2. There is no limit to the method name. The first parameter must contain this;

3. namespace system can be used for the namespace of the extension method, but it is not recommended;

4. The class defining the extension method is a static class;

 

After the method is extended by using this parameterProgram During compilation, the Assembly will add something similar to the following on the corresponding static class. This makes it easy to find a call. [Attributeusage (attributetargets. Method | Attributetargets. Class | Attributetargets. Assembly)]
Public   Sealed   Class Extensionattribute: attribute
{
......
}

In msil, the followingCode : . Custom instance Void [System. Core] system. runtime. compilerservices. extensionattribute:. ctor () = ( 01   00   00   00 ) We can see that system. Core. dll must be referenced during runtime.

 

Reference Source:

C # extension methods under advanced methods

C # features-Extension Method

C # amazing use of extension methods