ShowDialog using invoke is making the application unresponsive

Question

I'm using Control.Invoke() to show a dialog. The code is a handler to get credentials from the user and it can be execute in a thread, this is the reason I perform the call into an InvokeRequired/Invoke snippet.

Sometimes, and only in some machines, when I close the dialog, the application becomes unresposive (it does not manage some mouse clicks, but manage others). If I execute some "allowed" actions, the application start to be responsive again. It seems that processing any event, the application fixes itself.

Do you know any known bug in the .NET framework, or something that could cause this issue?

Thanks in advance.

---

EDIT: This is the code I'm using:

public class GuiCredentialsHandler
{
    // control used to invoke if needed
    private static Control mInvokeControl;

    // control used as parent for showDialog (could be null)
    private static Control mParentControl;

    /// <summary>
    /// Initialize a GetCredentials handler for current process.
    /// This method should be always called from the UI thread, for
    /// a correctly handling for invokes (when the handler is called
    /// from a thread).
    /// </summary>
    /// <param name="parentControl">Application top form. 
    /// Can be null if unknown</param>
    public static void Initialize(Control parentControl)
    {
        if (parentControl != null)
        {
            mInvokeControl = parentControl;
        }
        else
        {
            mInvokeControl = new Control();
            // force to create window handle
            // otherwise, invoke required always
            // return false
            mInvokeControl.CreateControl();
        }

        mParentControl = parentControl;
    }

    public static Credentials GetCredentials(
        string servername, SEIDWorkingMode serverWorkingMode)
    {
        if (mInvokeControl.InvokeRequired)
        {
            return mInvokeControl.Invoke(
                new GetCredentialsDelegate(DoGetCredentials),
                new object[] { servername, serverWorkingMode })
            as Credentials;
        }
        else
        {
            return DoGetCredentials(servername, serverWorkingMode);
        }
    }

    private static Credentials DoGetCredentials(
        string servername, SEIDWorkingMode serverWorkingMode)
    {

        GetCredentialsDialog dialog = new GetCredentialsDialog();

        dialog.Server = servername;
        dialog.WorkingMode = serverWorkingMode;

        DialogResult result = dialog.ShowDialog(mParentControl);

        if (result == DialogResult.Cancel) return null;

        UserInfoRetriever retriever = new UserInfoRetriever(
            servername, serverWorkingMode,
            dialog.UserName, dialog.Password);

        SEID seid = retriever.GetCurrentUser();

        return new Credentials(seid, serverWorkingMode);
}

public delegate Credentials GetCredentialsDelegate(
    string serverName,
    SEIDWorkingMode mode);

Answer 1

Is Control.Invoke actually needed in this case?

I was always under the impression that invoke was used to ensure that UI elements are accessed by the thread that creates the control which is usually the UI thread but does not have to be.

In this case it looks like you are trying to create a dialog from a thread and hence you should be able to update it from the thread. (Obviously you can't access it from outside your thread, which will include the main UI thread).

If I'm wrong no doubt this will get downvoted very quickly.