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Kode 

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

namespace WindowsApplication1starttest
{
    public class Win32
    {
        // The WM_COMMAND message is sent when the user
        // selects a command item from a menu, 
        // when a control sends a notification message
        // to its parent window, or when an 
        // accelerator keystroke is translated.
        public const int WM_COMMAND = 0x111;
        public const int WM_CLOSE = 0x10 ;

        // The FindWindow function retrieves a handle
        // to the top-level window whose class name
        // and window name match the specified strings.
        // This function does not search child windows.
        // This function does not perform a case-sensitive search.
        [DllImport("User32.dll")]
        public static extern int FindWindow(string strClassName,
                                                 string strWindowName);

        // The FindWindowEx function retrieves
        // a handle to a window whose class name 
        // and window name match the specified strings.
        // The function searches child windows, beginning
        // with the one following the specified child window.
        // This function does not perform a case-sensitive search.
        [DllImport("User32.dll")]
        public static extern int FindWindowEx(int hwndParent,
            int hwndChildAfter, string strClassName, string strWindowName);


        // The SendMessage function sends the specified message to a 
        // window or windows. It calls the window procedure for the specified 
        // window and does not return until the window procedure
        // has processed the message. 
        [DllImport("User32.dll")]
        public static extern Int32 SendMessage(
            int hWnd,               // handle to destination window
            int Msg,                // message
            int wParam,             // first message parameter
            [MarshalAs(UnmanagedType.LPStr)] string lParam);
        // second message parameter

        [DllImport("User32.dll")]
        public static extern Int32 SendMessage(
            int hWnd,               // handle to destination window
            int Msg,                // message
            int wParam,             // first message parameter
            int lParam);            // second message parameter

        public Win32()
        {

        }

        ~Win32()
        {
        }
    }

}

Kode 

 int ihandle = Win32.FindWindow(null, "EymBCrdCMD");
                Win32.SendMessage(ihandle, Win32.WM_CLOSE,0x0,0x0);