protected override void OnStartup(StartupEventArgs e)
{
base.OnStartup(e);
ShellWindow shellWindow = new ShellWindow();
StartWindow startWindow = new StartWindow();
Task.Run(() =>
{
Thread.Sleep(3000);
this.Dispatcher.Invoke(() =>
{
startWindow.Close();
});
});
startWindow.ShowDialog();
shellWindow.Show();
}