hide external app from taskbar
private const int SW_HIDE = 0x00;
private const int SW_SHOW = 0x05;
private const int WS_EX_APPWINDOW = 0x40000;
private const int GWL_EXSTYLE = -0x14;
private const int WS_EX_TOOLWINDOW = 0x0080;
private static void HideAppinTaskBar()
{
var Handle = FindWindowByCaption(IntPtr.Zero, "Untitled - Notepad");
ShowWindow(Handle, SW_HIDE);
SetWindowLong(Handle, GWL_EXSTYLE, GetWindowLong(Handle, GWL_EXSTYLE) | WS_EX_TOOLWINDOW);
ShowWindow(Handle, SW_SHOW);
}