public const int BM_CLICK = 0x00F5;
[DllImport( "user32.dll", CharSet = CharSet.Auto, SetLastError = true )]
static extern IntPtr FindWindowEx( IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow );
[DllImport( "user32.dll", CharSet = CharSet.Auto, SetLastError = true )]
private static extern IntPtr SendMessage( IntPtr hwnd, uint Msg, IntPtr wParam, IntPtr lParam );
private void button1_Click( object sender, EventArgs e ) {
IntPtr buttonHandle = FindWindowEx( Process.GetCurrentProcess().MainWindowHandle, IntPtr.Zero, null, "button4" );
SendMessage( buttonHandle, BM_CLICK, IntPtr.Zero, IntPtr.Zero );
}
private void button4_Click( object sender, EventArgs e ) {
MessageBox.Show( "Test" );
}