Question

I am experiencing a very weird problem: In WPF I have a tabControl which contains 3 tabItems. I have made a binding from the tabControl’s SelectedIndex to a property inside my viewModel class in “OneWayToSource” mode.

Here’s the XAML code:

<TabControl Name="mainTabControl" SelectedIndex="{Binding SelectedTabIndex, Mode=OneWayToSource}"  >
        <TabItem Header="Tab 01" Name="tab01"> ... </TabItem>
        <TabItem Header="Tab 02" Name="tab02"> ... </TabItem>
        <TabItem Header="Tab 03" Name="tab03"> ... </TabItem>
</TabControl>

And in my viewModel:

    private int m_selectedTabIndex;
    public int SelectedTabIndex
    {
        get
        { return m_selectedTabIndex; }
        set
        {
            SetAndNotify(ref m_selectedTabIndex, value, () => SelectedTabIndex);
            SelectedTabChanged();
        }
    }

private void SelectedTabChanged()
    {
        // Some code
    }

As you can see, everytime my viewModel’s SelectedTabIndex property changes, the SelectedTabChanged() method is executed, this works perfectly.

My weird problem is that: When I show a message using for example System.Windows.MessageBox.Show("Some Text") inside my SelectedTabChanged() method, I select another tabItem and the previous selected tab gets blocked, it looks like selected, but it remains selected permanently, I cannot see its content anymore.

Just to clarify: As I stated before, this weird issue only happens when a modal window is showed

Why is happening? How can I solve this issue?

I hope I explained myself clearly.

Thank you in advance.

Answer 1

I have solved my problem. Since I am new in WPF I really dont understand why a modal window make the tabs get blocked. But I was searching and found that the Dispatcher class allows one to execute asynchronously a method which prevent any control from get blocked.

I changed my viewModel code as below:

public int SelectedTabIndex
    {
        get
        { return m_selectedTabIndex; }
        set
        {
            SetAndNotify(ref m_selectedTabIndex, value, () => SelectedTabIndex);
            Dispatcher.CurrentDispatcher.BeginInvoke(new Action(SelectedTabChanged), null);
        }
    }

The line that really helped me was the following:

Dispatcher.CurrentDispatcher.BeginInvoke(new Action(SelectedTabChanged), null);

Hope this help someone else can be experiencing some similar problem.