C# - How to set the property to Ui Thread

Question

I'm getting an error (Exception from HRESULT: 0x8001010E (RPC_E_WRONG_THREAD)).
What should be the problem here, my senior dev said I need to set it to the UI Thread, here's my code:

private bool CanPrintReceipt() {
    return _receipt != null && !IsBusy;
}

private async void PrintReceipt() {
    IsBusy = true;
    try {
        await _printReceiptInteractor.PrintTerminalReceiptAsync(_receipt).ConfigureAwait(false);
        Dispatcher.Dispatch(() => {
            this.Close();
        });
    } catch (Exception e) {
        _log.Error($"{nameof(PrintReceipt)}: ", e);
        await this._dialogService
            .ShowMessageOKAsync(e.Message, "Printer Error");
    } finally {
        IsBusy = false; // but when i set this to true , no error
    }
}

I'm having error in my other class,

    public void RaisePropertyChanged([CallerMemberName]string propertyName = null)
    {
        if (Windows.ApplicationModel.DesignMode.DesignModeEnabled)
            return;

        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); //here it shows that error
    }

What do you guys think the problem is? There is no RunAsync, I saw that's the other solution
Thanks,
Nico

Yep, and removed it after http://stackoverflow.com/q/38759257/251311 — zerkms, Aug 05 '16 at 03:25
im sorry , bu i really dont know , i just make that a try catch statement. btw that method print the receipt — Reaper, Aug 05 '16 at 03:28
Possible duplicate of [Update UI from thread in WinRT](http://stackoverflow.com/questions/9540260/update-ui-from-thread-in-winrt) — Bart, Aug 05 '16 at 06:46

score 2 · Accepted Answer · answered Aug 05 '16 at 03:35

The problem is with .ConfigureAwait(false).

What it does is sets continueOnCapturedContext to false, which means it not necessary will be the same thread to continue evaluate the function after awit that invoked the asynchronous function.

So in your case you don't need it, because that's exactly what you need - to restore in the same thread after it's done.

And in general, the simple rule of thumb is:

You use .ConfigureAwait(false) in the library code that is general purpose and does not deal with UIs
You don't use it otherwise.

Details: MSDN - Async/Await - Best Practices in Asynchronous Programming

thanks , btw already fixed it , and yeah its because of the ConfigureAwait — Reaper, Aug 17 '16 at 01:21

C# - How to set the property to Ui Thread

1 Answers1