Interview Questions

How do you directly call a native function exported from a DLL?

C# Interview Questions and Answers

(Continued from previous question...)

10. How do you directly call a native function exported from a DLL? 

Here’s a quick example of the DllImport attribute in action:

using System.Runtime.InteropServices; \
class C
{
	[DllImport(\"user32.dll\")]
public static extern int MessageBoxA
(int h, string m, string c, int type);
	public static int Main()
	{
return MessageBoxA(0, \"Hello World!\", \"Caption\", 0);
	}
}

This example shows the minimum requirements for declaring a C# method that is implemented in a native DLL. The method C.MessageBoxA() is declared with the static and external modifiers, and has the DllImport attribute, which tells the compiler that the implementation comes from the user32.dll, using the default name of MessageBoxA. For more information, look at the Platform Invoke tutorial in the documentation.

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