c# Delegate Throws System.InvalidOperationException

Question

I have a Thread that retrieves infos from an xml file. In my main form I have a checkbox that in case a boolean in the xml is true must be checked by the thread. I have created a Delegate but despite this when the thread tries to change the value of the checkbox a System.InvalidOperationException is thrown. Why ?!?

private delegate void ProjectFileReloadDelegate(string pp);

private void ProjectFileReload(string projectPath)
{
    if (this.InvokeRequired)
    {
        this.Invoke(new ProjectFileReloadDelegate(ProjectFileReload), projectPath);
    }
    else
    {
        //This throws the exception
        //I retrive the anchorMode Info 
        anchorMode.Checked = ProjectOptions_v000.AnchorMode;
    }

Answer 1

On one of my projects, which handled quite a few API, I used Task to handle async api calls. Due to the uncertainty on weather it would be on Main GUI thread or another I used Task.Factory.StartNew with a TaskScheduler.FromCurrentSynchronizationContext() as parameter to handle any code updating the GUI. The reference for this is from Microsoft the section titled "Specifying a synchronization context" The TaskScheduler.FromCurrentSynchronizationContext() tells it run on gui thread.

This is how I would update your code to prevent Exceptions from updating GUI content on other threads.

    private delegate void ProjectFileReloadDelegate(string pp);

    private void ProjectFileReload(string projectPath)
    {
        if (this.InvokeRequired)
        {
            this.Invoke(new ProjectFileReloadDelegate(ProjectFileReload), projectPath);
        }
        else
        {
            //This throws the exception
            //I retrive the anchorMode Info 

            Task.Factory.StartNew(
                       delegate {
                           anchorMode.Checked = ProjectOptions_v000.AnchorMode;
                       }, TaskScheduler.FromCurrentSynchronizationContext()
                   );