Issues calling Dispatcher in WPF

Question

I have some UI code that needs to be updated from my background presenter thread. So, I do the following: from my background thread, I set my property in the UI: _ui.ConnectionStatus = "A";

then, my set is as follows:

public string ConnectionStatus

{

set{

if (Dispatcher.CheckAccess())

ConnectionStatusTxt.Content = value;

else {

Dispatcher.Invoke(DispatcherPriority.Normal, (Action)(() =>
                                  {ConnectionStatusTxt.Content = value;}));

}

} }

I get the following error: "The calling thread cannot access this object because a different thread owns it." My understanding was that Dispatcher takes care of invoking on different threads, so this error puzzles me a little. Thanks!

Answer 1

You don't say what object this setter is executing inside, but it looks like this object's Dispatcher is not the same as ConnectionStatusTxt's dispatcher, i.e. the object containing the setter is owned by a different thread from the ConnectionStatusTxt control.

Try using ConnectionStatusTxt.Dispatcher in your CheckAccess and Invoke statements.

Answer 2

Another question: what type is value? is this a string? I could imagine that the error might be that value is in fact a UIElement (maybe a Label?) that you create in which case the exception refers to the value object and not to your user control.