C# Thread-safe Extension Method

Posted by Wonko the Sane on Stack Overflow See other posts from Stack Overflow or by Wonko the Sane
Published on 2010-04-05T21:29:34Z Indexed on 2010/04/05 21:33 UTC
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Hello All,

I may be waaaay off, or else really close. Either way, I'm currently SOL. :)

I want to be able to use an extension method to set properties on a class, but that class may (or may not) be updated on a non-UI thread, and derives from a class the enforces updates to be on the UI thread (which implements INotifyPropertyChanged, etc).

I have a class defined something like this:

public class ClassToUpdate : UIObservableItem
{
    private readonly Dispatcher mDispatcher = Dispatcher.CurrentDispatcher;
    private Boolean mPropertyToUpdate = false;

    public ClassToUpdate() : base()
    {
    }

    public Dispatcher Dispatcher
    {
        get { return mDispatcher; }
    }

    public Boolean PropertyToUpdate
    {
        get { return mPropertyToUpdate; }
        set { SetValue("PropertyToUpdate", ref mPropertyToUpdate, value; }
    }
}

I have an extension method class defined something like this:

static class ExtensionMethods
{
    public static IEnumerable<T> SetMyProperty<T>(this IEnumerable<T> sourceList,
                                                  Boolean newValue)
    {
       ClassToUpdate firstClass = sourceList.FirstOrDefault() as ClassToUpdate;

       if (firstClass.Dispatcher.Thread.ManagedThreadId != 
           System.Threading.Thread.CurrentThread.ManagedThreadId)
        {
            // WHAT GOES HERE?
        }
        else
        {
            foreach (var classToUpdate in sourceList)
            {
               (classToUpdate as ClassToUpdate ).PropertyToUpdate = newValue;
               yield return classToUpdate;
            }
        }
    }
}

Obviously, I'm looking for the "WHAT GOES HERE" in the extension method.

Thanks, wTs

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