Question

How do you directly call a native function exported from a DLL? Can someone just give me a small example?

Answer 1

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.

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