Thread abort exception occurs randomly

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C#

.NET

threads

VSTO

AddIn

, +

Hi,

I am working on excel plugin, when I need to show a spinner till some operation happens in the background. I took an approach where I have placed the spinner image(gif) in another windows form and call it in a separate thread. Once the operation gets complete, I abort this thread which is running the spinner form.

This is giving thread abort exception randomly.

What I have tried:

Here is my code:

Spinner form:

<pre>public partial class LoadingScreen : Form
    {
        private LoadingScreen _loadingScreen = null;
        private Thread oThread = null;

        public LoadingScreen()
        {
            InitializeComponent();
        }

        public LoadingScreen(bool showloading)
        {
            InitializeComponent();

            ShowLoadingScreen();
        }
        public void FocusLoading()
        {
            if (_loadingScreen == null)
                ShowLoadingScreen();
            if (oThread != null)
            {
                this.Activate();
            }
        }
        private void ShowFormOpacity()
        {
            _loadingScreen = new LoadingScreen();
            _loadingScreen.Opacity = .75;
            _loadingScreen.Controls["lblLoading"].Visible = false;
            if (_loadingScreen != null)
                Application.Run(_loadingScreen);
        }

        public void CloseFormInstance()
        {
            if (oThread != null)
            {
                try
                {
                    _loadingScreen = null;
                    oThread.Abort();
                    oThread.Join();
                }
                catch (Exception ex) { }
            }
        }
        public void ShowLoadingScreen()
        {
            if (_loadingScreen != null)
                return;
            oThread = new Thread(new ThreadStart(ShowFormOpacity));
            oThread.IsBackground = false;
            oThread.SetApartmentState(ApartmentState.STA);
            oThread.Start();
            while (_loadingScreen == null || _loadingScreen.IsHandleCreated == false)
            {
                System.Threading.Thread.Sleep(50);
            }
        }
    }

Calling the spinner form from ThisAddIn.cs

private LoadingScreen screen;

public void LoadingScreen(bool showloading)
{
    if (screen != null)
    {
        screen.FocusLoading();
    }
    else
    {
        screen = new LoadingScreen(showloading);
    }
}
public void CloseFormInstance()
{
    if (screen != null)
    {
        screen.CloseFormInstance();
    }
}

Why is the thread abort exception happens sometimes?