BackgroundWorker - Calling thread cannot access object

Question

So in my DoWork, I have

List<KeyValuePair<String, BitmapImage>> Files = new List<KeyValuePair<string,BitmapImage>>((List<KeyValuePair<String, BitmapImage>>)e.Argument);

foreach (KeyValuePair<String, BitmapImage> i in Files)
{
    string temp = i.ToString();               .......(1)
    //.....
}

I'm passing the argument as follows :-

backgroundWorkerForReupload.RunWorkerAsync(files);

where "files" is of Type List<KeyValuePair<string, BitmapImage>>

At line (1) above, it throws an InvalidOperationException with the message : " The calling thread cannot access this object because a different thread owns it. "

I'm confused as to why i is owned by another thread. Any help would be greatly appreciated. Thank you.

Answer 1

Most WPF objects, including BitmapImage , are thread-affine, and can only be used by the thread they were created on.

You can fix this for BitmapImage by calling Freeze() first.