Question

I have an issue regarding cross thread calls in WPF.

            foreach (RadioButton r in StatusButtonList)
        {
            StatusType status = null;
            r.Dispatcher.Invoke(new ThreadStart(() => status= ((StatusButtonProperties)r.Tag).StatusInformation));
            if (AppLogic.CurrentStatus == null || AppLogic.CurrentStatus.IsStatusNextLogical(status.Code))
            {
                SolidColorBrush green = new SolidColorBrush(Color.FromRgb(102, 255, 102));
                r.Dispatcher.Invoke(new ThreadStart(() =>  r.Background = green));
            }
            else
            {
                SolidColorBrush red = new SolidColorBrush(Color.FromRgb(255, 0, 0));
                r.Dispatcher.Invoke(new ThreadStart(() => r.Background = red));
            }
        }

When I run this code, it works correctly for the first iteration. However during the second iteration the line:

  r.Dispatcher.Invoke(new ThreadStart(() => status= ((StatusButtonProperties)r.Tag).StatusInformation))

Causes this exception:

Cannot use a DependencyObject that belongs to a different thread than its parent Freezable.

I’ve tried a few solutions but I can’t find anything workable.

Any help appreciated!

Answer 1

I’d rewrite this to:

r.Dispatcher.Invoke(new Action(delegate()
{
    status = ((StatusButtonProperties)r.Tag).StatusInformation;

    if (AppLogic.CurrentStatus == null || AppLogic.CurrentStatus.IsStatusNextLogical(status.Code))
    {
        r.Background = Brushes.Green;
    }
    else
    {
        r.Background = Brushes.Red;
    }

}));