Following is the example to use it properly This is from msdn for more visit
http://msdn2.microsoft.com/en-us/library/system.runtime.interopservices.dllimportattribute.aspx


using System;
using System.Runtime.InteropServices;

class Example
{
 // Use DllImport to import the Win32 MessageBox function.
 [DllImport("user32.dll" CharSet CharSet.Auto)]
 public static extern int MessageBox(IntPtr hWnd String text String caption uint type);
 
 static void Main()
 {
  // Call the MessageBox function using platform invoke.
  MessageBox(new IntPtr(0) "Hello World!" "Hello Dialog" 0);
 }
}