Help with "owned" variables concept in WPF

Question

I'm trying to move from WinForms to WPF and so far it's been going well. I'm struggling with the concept of updating variables from events in my code behind. It says that it was created or owned by another thread. Basically in my code all over the place I am
having to put:
this.Dispatcher.Invoke((Action)(() => { //Code Here }));
Generally this is happening from an async call to update some data.
Am I doing something fundamentally wrong in my design?
If this snippet of code is the solution, how do I understand without the runtime compiler telling me, when I should be doing it?
Can you explain what is happening with the Dispatcher.Invoke ((Action)(() =>{}));
My thinking so far
(Action) is casting the (() => {}) to an action object
() is creating a nameless function?
=> {} define the function right here, we could have pointed to a real function if we wanted.
Thanks for any education you can give me.

Answer 1

The thing is that you can only update a UI element on the thread on which it was created. This rule applies to both Windows Forms and WPF. Please refer to the following great article for more information about the threading model in WPF:
https://msdn.microsoft.com/en-us/magazine/cc163328.aspx. You should only create UI elements (TextBoxes, Buttons, etc.) on the UI thread and not on any background thread.
>>Can you explain what is happening with the Dispatcher.Invoke ((Action)(() =>{}));
The delegate (Action) that you pass to the Invoke method will be executed on the UI (or dispatcher) thread. Please refer to the above article for more information.
>>If this snippet of code is the solution, how do I understand without the runtime compiler telling me, when I should be doing it?
The Dispatcher has a CheckAccess() method that returns false if you are required to call the Invoke method, i.e. if the current thread doesn't have access to the UI object. You could just call this one before you call the Invoke method:
if (!Dispatcher.CheckAccess())
Dispatcher.Invoke(new Action(() => { }));
Hope that helps.
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