Question

hello i got a problem, whenever i try to write any simple thing inside the TabControl_SelectionChanged event i am getting this message

An unhandled exception of type ‘System.InvalidOperationException’ occurred in WindowsBase.dll

Additional information: Dispatcher processing has been suspended, but messages are still being processed.

for example: this is my xaml:

<Window x:Class="try1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="auto" Width="auto" xmlns:my="clr-namespace:try1" mc:Ignorable="d" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" d:DesignHeight="171" d:DesignWidth="271" SizeToContent="WidthAndHeight">
<TabControl SelectionChanged="TabControl_SelectionChanged">
    <CheckBox Name="cbx"></CheckBox>
    <TabItem Header="tabItem1" Name="tabItem1">
        <Grid />
    </TabItem>
    <TabItem Header="tabItem2" Name="tabItem2">
        <Grid />
    </TabItem>
</TabControl>

and this is my code behind :

private void something_Click(object sender, RoutedEventArgs e)
    {
        MessageBox.Show("hello");

    }

thanks in advance for your help

Answer 1

That’s because you SelectionChanged event gets fired before the tabcontrol (and window) is loaded.
If you do it like this, it works (sorry for the VB.NET sample, but you get the point):

Private Sub TabControl_SelectionChanged(ByVal sender As Object, ByVal e As RoutedEventArgs)

    If Me.IsLoaded Then
        MsgBox("hello")
    End If

End Sub

And yes, the reason is explained in the newsgroup post mentioned in the comment.