i am using a backgroundWorker to do a long running operation:

BackgroundWorker backgroundWorker = new BackgroundWorker() { WorkerSupportsCancellation = true, WorkerReportsProgress = true };

backgroundWorker.RunWorkerCompleted += delegate(object s, RunWorkerCompletedEventArgs args)
{

};

backgroundWorker.ProgressChanged += delegate(object s, ProgressChangedEventArgs args)
{
    someViewModel.SomeProperty.Add((SomeObject)args.UserState);
};

backgroundWorker.DoWork += delegate(object s, DoWorkEventArgs args)
{
    someViewModel.SomeList.ForEach(x =>
    {
        someViewModel.SomeInterface.SomeMethod(backgroundWorker, someViewModel, someViewModel.SomeList, x);
    });
};

backgroundWorker.RunWorkerAsync();

Then in SomeInterface.SomeMethod:

public void SomeMethod(BackgroundWorker backgroundWorker, SomeViewModel someViewModel//....)
{
    //Filtering happens

    backgroundWorker.ReportProgress(0, someObjectFoundWhileFiltering);
}

So, when it comes to:

backgroundWorker.ProgressChanged += delegate(object s, ProgressChangedEventArgs args)
{
    someViewModel.SomeProperty.Add((SomeObject)args.UserState);//Adding the found object to the Property in the VM
};

On the line someViewModel.SomeProperty.Add((SomeObject)args.UserState);, the set on the Property is not firering and the UI just locks up.

What am i doing wrong? Is this the correct way to update the UI thread?