Question

I have only been working with C# for a few weeks and I have gotten stuck on a threading issue.

I’ve been building a custom slideshow that implements a .ppt presentation hosted in a winform handled by an independent class. The slideshow switches off with another program that displays dynamic data from a shop floor. This second program needs to be sent a command to enter full screen mode as I do not have access to it’s source code.

Using Setforegroundwindow API I can easily switch between the two applications and control the power point with the COM interface but the transition is choppy with screens resizing. I would like to overlay a blank black winform that fades in and out while this transition occurs. So far I have been unsuccessful in doing this smoothly, I have tried running the fading form and transition on separate threads but I haven’t got it quite figured out. If anyone might have any advice on how to do this it would be much appreciated.

Thank you.

Answer 1

After working through some example code I implemented a background worker that did the trick. For more info From msdn – How to: Use a Background Worker.

I’m trying to find a more reliable way to ensure the F11 command is processed by the application, but for now I’ve put in a Thread.Sleep before the SendKeys.

Please feel free to leave comments or questions.

[DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool SetForegroundWindow(IntPtr hWnd);

    Process p;
    //Process p is initialized: p = Process.Start(@"<path\application.exe>");
    Form2 oForm;

 private void transition()
    {
        BackgroundWorker bw = new BackgroundWorker();
        oForm = new Form2();

        bw.DoWork += new DoWorkEventHandler(bw_DoWork);
        bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
        oForm.Show();
        if (bw.IsBusy != true)
        {
            bw.RunWorkerAsync();
        }

    }
    private void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {       
        oForm.closethis();
    }
    private void bw_DoWork(object sender, DoWorkEventArgs e)
    {
        BackgroundWorker worker = sender as BackgroundWorker;

            if ((worker.CancellationPending == true))
            {
                e.Cancel = true;                   
            }
            else
            {                   
                SetForegroundWindow(p.MainWindowHandle);
                p.WaitForInputIdle(3000);
                System.Threading.Thread.Sleep(500);
                SendKeys.SendWait("{F11}");    
                //Sends the application into full screen mode           
            }

    }

And the code for the form that fades in and out..

public partial class Form2 : Form
{
    public Form2()
    {
        this.Visible = false;
        this.Opacity = 0;

        InitializeComponent();

        this.TopMost = true; 
        this.Visible = true;

        while (this.Opacity < 1)
        {
           this.Opacity += .05;
           Thread.Sleep(5);
           this.TopMost = true;
        }       
    }
    private void closefade()
    {
        while (this.Opacity > 0)
        {
            this.Opacity -= .05;
            Thread.Sleep(5);
            this.TopMost = true;
        }
        this.Close();
    }

    delegate void CloseBack();
    public void closethis()
    {
        if (this.InvokeRequired)
        {
            CloseBack b = new CloseBack(closethis);
        }
        else
            closefade();
    }
}