C # extern modifier Overview

This section describes how to use the C # extern modifier and DllImport together with the static modifier. It can also be used for calling components of different versions of the same assembly and cannot be used together with the abstract modifier.

 

C # is a common language. Here we mainly introduce the C # extern modifier, including the member functions that are often used to call system API functions.

 

What does the C # extern modifier mean?

 

The C # extern modifier is used to declare that member functions implemented outside the Assembly are often used to call system API functions (through DllImport ). Note: when using the C # extern modifier and DllImport together, you must add a static modifier. It can also be used for calling components of different versions of the same assembly (using extern to declare aliases) it cannot be used together with the abstract modifier.

 

Example:

 

  
  

   
   
Using System;
   
   
Using System. Collections. Generic;
   
   
Using System. Text;
   
   
Using System. Runtime. InteropServices;
   
   

   
   
Namespace Example03
   
   
{
   
   
Class Program
   
   
{
   
   
// Note that DllImport is an Attribute Property,
   
   
// Defined in the System. Runtime. InteropServices namespace
   
   
// A static modifier must be added when the extern and DllImport are used together.
   
   
[DllImport ("User32.dll")]
   
   
Public static extern int
   
   
MessageBox (int Handle, string Message, string Caption, int
   
   
Type );
   
   
Static int Main ()
   
   
{
   
   
String myString;
   
   
Console. Write ("Enter your message :");
   
   
MyString = Console. ReadLine ();
   
   
Return MessageBox (0, myString, "My Message Box", 0 );
   
   
}
   
   
}
   
   
}