CODEWITHSUNDEEP
c#wpfmvvminvalidoperationexception
baptiste
baptiste

Reputation: 1169

InvalidOperationException, the calling thread should be STA because

I am developping a project in order to manipulate a lot of objects with several modalities (mouse, leapmotion, touch ...). I made it using the MVVM pattern soI have several Views and ViewModels for all the components I will use. To make it easier to develop I chose to have a Canvas component in which I will manipulate Grids. Each Grid can contain any type of object (Shape, Text, Image, Documents...).

To be able to have all modalities linked to my method, I decided to build one listener per modality (1 for the mouse, 1 for the leapmotion...) and make them detect basic gestures (as Click, DoubleClick ...). All the gestures I chose to detect are associate with a method via a Dictionary. Anyway the linking is working as expected as it executes the right method. T o give an example I have the action calling in my mouse listener:

if (_leftClickCounter == 1 && _capturedLeft == false)
{
    if (_dic.ContainsKey(Key.OnClick))
    {
        Action<object> action = _dic[Key.OnClick];
        action.Invoke(null);
    }
}

Where:

In my example the method executed is:

public void Add(object sender)
{
    ObjectModel objectModel = new ObjectModel();
    ObjectView objectView = new ObjectView(objectModel);
    this.objectViews.Add(objectView);
}

Where sender is just used for test purpose. It remains unused in the method. My execution stops when it tries to instanciate my ObjectView saying:

InvalidOperationException
The calling thread must be STA, because many UI components require this

My ObjectView.xaml.cs class is:

public partial class ObjectView : UserControl
{
    public ObjectView(ObjectModel obj)
    {
        InitializeComponent();

        EventLinker linker = new EventLinker(this.visualBox);
        ObjectViewModel objectVM = new ObjectViewModel(obj, linker);
        this.DataContext = objectVM;
    }
}

And its ObjectView.xaml defining the UserControl to use is very basic:

<UserControl x:Class="AusyTouchMultimodal_v1.View.ObjectView"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
     mc:Ignorable="d" 
     d:DesignHeight="300" d:DesignWidth="300">

     <Grid x:Name="visualBox" Background="Blue"/>

</UserControl>

I dont have any compilation errors, just this InvalidOperationException. Can someone explain this issue to me?

Thanks!

Upvotes: 1

Views: 452

Answers (1)

Matija K.
Matija K.

Reputation: 305

Try calling your actions in ui thread, like this

if (_leftClickCounter == 1 && _capturedLeft == false)
{
    if (_dic.ContainsKey(Key.OnClick))
    {
        Action<object> action = _dic[Key.OnClick];
        // action.Invoke(null);         
        System.Windows.Application.Current.Dispatcher.BeginInvoke( call your action )
    }
}

Upvotes: 2

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