CODEWITHSUNDEEP
c#.netwpf
Vaccano
Vaccano

Reputation: 82507

Non-UI "The calling thread cannot access this object because a different thread owns it"

I have the following code:

var queue = printer.PrintQueue;
var canPrint = ! Dispatcher.CurrentDispatcher.Invoke(()
                            => queue.IsPaperJammed || queue.IsOutOfPaper || 
                               queue.IsInError || queue.HasPaperProblem);

It is throwing the following error:

The calling thread cannot access this object because a different thread owns it

I have tried this on UI thread (using the dispatcher as shown above) and I have tried it on the current thread (without the dispatcher).

Is there a way to ask a object which thread owns it?

Upvotes: 3

Views: 879

Answers (3)

Hakan Fıstık
Hakan Fıstık

Reputation: 19511

just crazy as it is, the following code did not work, and it still throws the exception

dlg.PrintTicket.PageMediaSize = new PageMediaSize(302.36220472, int.MaxValue);
dlg.PrintTicket.PageOrientation = PageOrientation.Portrait;

but this code worked

dlg.PrintTicket = new PrintTicket()
{
    PageMediaSize = new PageMediaSize(273, int.MaxValue),
    PageOrientation = PageOrientation.Portrait,
};

of course the both code must be in Application.Current.Dispatcher.Invoke(() => {}) but still the first will throw the exception and the second will solve the problem

Upvotes: 0

Wonderbird
Wonderbird

Reputation: 374

There is a way to determine if the CURRENT thread owns a control:
Use control.Dispatcher.CheckAccess() to check whether the current thread owns the control. If it does not own it then Invoke an Action using dispatcher.

Upvotes: 0

har07
har07

Reputation: 89325

Have you tried without CurrentDispatcher ? :

var canPrint = ! Application.Current.Dispatcher.Invoke(()
                            => queue.IsPaperJammed || queue.IsOutOfPaper || 
                               queue.IsInError || queue.HasPaperProblem);

CurrentDispatcher.Invoke() will invoke your code from the thread currently executing, it is non-UI thread assuming that snippet in this question is run from non-UI thread.

References :

Upvotes: 4

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