Cant select Items in Listbox when using Tabcontrol

问题:

I have a problem with the selection of items in a Listbox, when the Listbox is in a Tabcontrol. I can't select any item in the Listbox. I am filling the Listbox dynamically via code-behind, also I am using drag and drop on it, though, Drag and drop is working with the tabcontrol.

Here is my XAML code:

<Window x:Class="SPInstallApp.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:toolkit="clr-namespace:Microsoft.Windows.Controls;assembly=WPFToolkit.Extended"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="SharePoint 2010 - wspSync" Height="450" Width="700" AllowDrop="True" Icon="/SPInstallApp;component/Images/favicon.ico">

<Window.Resources>
    <DataTemplate x:Key="CustomListBoxTemplate">
        <StackPanel>
            <Grid Margin="4">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="48 "/>
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                </Grid.RowDefinitions>
                <Image Source="{Binding Path=ImageSource}" Grid.Column="0" Grid.RowSpan="3" Margin="0,0,5,0" />
                <TextBlock 
              Padding="0,5,0,0"
              Text="{Binding Path=Title}" 
              Grid.Column="1" 
              Grid.Row="0" 
              FontWeight="Bold"/>
                <TextBlock
              Padding="0,0,0,5"
              Text="{Binding Path=Description}" 
              Grid.Column="1" 
              Grid.Row="1"
              FontStyle="Italic" />
                <TextBlock
              Padding="0,0,0,5"
              Text="{Binding Path=Status}"                  
              Grid.Column="1" 
              Grid.Row="2"
              FontStyle="Italic" Foreground="#FFDE2B2B" />
            </Grid>                
        </StackPanel>
    </DataTemplate>
</Window.Resources>
<toolkit:BusyIndicator IsBusy="True" BusyContent="Bitte warten..." Name="busyIndicator">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="50"/>
        </Grid.RowDefinitions>
        <Label Content="Websitecollection wählen:" Grid.Row="0" Grid.Column="0" Margin="5,0,0,0"  />
        <ComboBox Grid.Row="1" Grid.Column="0" Height="20" Margin="10,0,10,10" Name="cbWebsitecollection" SelectionChanged="CbWebsitecollectionSelectionChanged" />
        <TabControl Grid.Row="2" Grid.Column="0" Name="tc" SelectionChanged="TcSelectionChanged" Margin="10,0,10,0">
            <TabItem Header="Installieren">
                <ListBox AllowDrop="True" Background="#CCC" Drop="ListBoxDrop" Name="lbDropbox" IsSynchronizedWithCurrentItem="True" ItemTemplate="{StaticResource CustomListBoxTemplate}" KeyUp="LbDropboxKeyUp" />
            </TabItem>
            <TabItem Header="Websitecollection">
                <CheckBox Content="test" />
            </TabItem>
        </TabControl>
        <Label Grid.Row="2" Grid.Column="0" VerticalAlignment="Center" HorizontalAlignment="Center" FontWeight="Bold" Content="drag 'n' drop" Margin="10" Drop="ListBoxDrop" Name="lbDescription" />
        <Button Grid.Row="3" Grid.Column="0" Name="cmdSync" Content="Synchronisieren" Margin="10" Width="100" HorizontalAlignment="Right" Click="CmdSyncClick" />
        <Image Grid.Row="3" HorizontalAlignment="Left" Name="Logo" Source="/SPInstallApp;component/Images/logo.gif" Margin="10" MouseUp="LogoMouseUp" MouseEnter="LogoMouseEnter" MouseLeave="LogoMouseLeave" />
    </Grid>
</toolkit:BusyIndicator></Window>

If i remove the Tabcontrol, everything is working. I hope someone can help me or know what the problem is.

greets

回答1:

I have found the problem. The problem is how Microsoft designed the MessageHandles. If a child of an item throws a message (for example selectionChanged) and the message is not handles, the message goes to the parent Item. So, in my case, if I click on an item in the ListBox, the (unhandled) message "selectionChanged" was sent to the TabControl, this was the problem. Because i have custom code in the TabControl.selectionChanged it always ran my code, instead of selecting the item in the ListBox.

The workaround is, to put this code in the selectionChanged eventhandler of the ListBox:

private void ListBox_selectionChanged(object sender, DragEventArgs e)
{
    e.handled = true;
}

This avoids the transfer of the message from the child messagehandler to the parent messagehandler.

I hope u can undersand my explanation.