[STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            using (frmSplash splash = new frmSplash())
            {
                splash.Text = String.Empty;
                splash.ControlBox = false;
                splash.StartPosition = FormStartPosition.CenterScreen;
                splash.ShowInTaskbar = false;
                splash.TopMost = true;

                splash.Show();
                splash.Update();
                //Application.DoEvents();

                //Simulation einer längeren Initialisierung
                for (int i = 0; i < 299; i++)
                {
                    Thread.Sleep(1);
                }

                //Thread.Sleep(5000);
                splash.Close();
            }


            using (Form1 frmHaupt = new Form1())
            {
                frmHaupt.StartPosition = FormStartPosition.CenterScreen;

                Application.Run(frmHaupt);
            }
        }

public partial class frmSplash : Form
    {
        private double myOpacity = 0.1;

        public frmSplash()
        {
            InitializeComponent();
        }

        private void timerFadeIn_Tick(object sender, EventArgs e)
        {
            myOpacity += 0.10;
            if (myOpacity ≥ 1)
            {
                this.Opacity = 1;
                timerFadeIn.Enabled = false;
                return;
            }
            this.Opacity = myOpacity;
            this.Update();
            //Application.DoEvents();
        }

        private void timerFadeOut_Tick(object sender, EventArgs e)
        {
            myOpacity-=0.10;
            if (myOpacity≤0.01)
            {
                timerFadeOut.Enabled = false;
                return;
            }
            this.Opacity = myOpacity;
        }

        private void frmSplash_Load(object sender, EventArgs e)
        {
            if (!SystemInformation.TerminalServerSession)
            {
                timerFadeIn.Interval = 5;
                timerFadeOut.Interval = 5;
                this.Opacity = myOpacity;
                timerFadeIn.Enabled = true;
                timerFadeOut.Enabled = false;
            }
        }

        private void frmSplash_FormClosing(object sender, FormClosingEventArgs e)
        {
            timerFadeOut.Enabled = true;
            timerFadeIn.Enabled = false;
        }
    }

public class Program
    {
        frmSplash splash;
        /// <summary>
        /// Der Haupteinstiegspunkt für die Anwendung.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            Program program = new Program();
            program.splash = new frmSplash();

            program.splash.Text = String.Empty;
            program.splash.ControlBox = false;
            program.splash.StartPosition = FormStartPosition.CenterScreen;
            program.splash.ShowInTaskbar = false;
            program.splash.TopMost = true;

            program.splash.Show();
            program.splash.Update();

            //HintergrundThread erstellen
            ParameterizedThreadStart threadstart = new ParameterizedThreadStart(program.longRunning);
            Thread worker = new Thread(threadstart);
            worker.IsBackground = true;
            //Wie bekomme ich einen Thread aus dem ThreadPool?
            bool test = worker.IsThreadPoolThread;

            worker.Start(9999);

            //warten bis HintergrundThread erstellt wurde
            while (!worker.IsAlive)
            {
                Thread.Sleep(1);
            }

            //warten bis HintergrundThread fertig ist
            worker.Join();

            //SplashScreen schließen
            program.splash.Close();

            //Hauptformular anzeigen
            using (Form1 frmHaupt = new Form1())
            {
                frmHaupt.StartPosition = FormStartPosition.CenterScreen;

                Application.Run(frmHaupt);
            }
        }

        private void longRunning(object parameter)
        {
            for (int i = 0; i < (int)parameter; i++)
            {
                Debug.WriteLine("Bin zurzeit bei: " + i.ToString());
                Thread.Sleep(1);
            }
        }
    }

                //Simulation einer längeren Initialisierung
                for (int i = 0; i < 299; i++)
                {
                    Thread.Sleep(1);
                }

private bool FadedIn = false;

// timerevent
if (this.Opacity < 1 && !FadedIn)
{
this.Opacty += 0.1;
}
else if (this.Opacity ≥ 1&& !FadedIn)
{
FadedIn = true;
// etl. wenn du auf ein ereignis warten willst bevor du raus fadest
Timer.enabled = true;
}
else if (this.Opacity > 0 && FadedIn)
{
this.Opacity -=0.1;
}