C# – Calling into Native DLLs

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P/Invoke, short for platform invocation services, allow you to access functions, structs, and callbacks in unmanaged DLLs.

Here, I’m able to import user32.dll, and then use a function inside user32.dll. Pretty cool, huh? Simply by naming a static method with the same name as the extern keyword, MessageBox, in our case, you can access functions within the DLL.

Compiled in Visual Studio 2017.

using System;
using System.Runtime.InteropServices;

class MessageBoxDLL
// call to which dll you would like to import
// our unmanaged dll

// our function
static extern int MessageBox(IntPtr hWnd, string text, string caption, int type);
// a static method with the same name as the function, i.e. MessageBox
public static void Main()
// calls function with relative parameters
// the marshaler does the translation for us
MessageBox(IntPtr.Zero,"This is a test!", "Yo", 0);



Marshaling Data with Platform Invoke

DllImportAttribute Class