WPF UI persistence in TabControl

Question

I am having issues with something that seems like it should be very simple but in fact has proven quite difficult.

Lets say you have a TabControl bound to an itemsource of ViewModels and the items displayed using a DataTemplate. Now lets say the DataTemplate consists of a Grid with two columns and a Grid splitter to resize the columns.

The problem is if you resize the columns on one tab, and switch to another tab, the columns are also resized. This is because the TabControl shares the DataTemplate among all tabs. This lack of UI persistence is applied to all elements of the template which can make for a frustrating experience when various UI components are adjusted. Another example is the scroll position in a DataGrid (on a tab). A DataGrid with few items will be scrolled out of view (only one row visible) if a DataGrid with more rows was scrolled to the bottom on another tab. On top of this, if the TabControl has various items defined in multiple DataTemplates the view is reset when you switch between items of differenet types. I can understand that this approach saves resources but the resultant functionality seems quite contradictory to expected UI behavior.

And so i'm wondering if there is a solution/workaround to this as i'm sure it's something that others have encountered before. I've noticed a few similar questions on other forums but there was no real solution. One about using the AdornerDecorator but that doesn't seem to work when used with a DataTemplate. I'm not keen on binding all the UI properties (like column width, scroll position) to my ViewModels and in fact I tried it for the simple GridSplitter example and I didn't manage to make it work. The width of the ColumnDefinitions were not necessarily affected by a grid splitter. Regardless, it would be nice if there were a general solution to this. Any thoughts?

If I ditch the TabControl and use an ItemsControl will I encounter a similar issue? Would it be possible to modify the TabControl Style so it doesn't share the ContentPresenter between tabs?

Answer 1

I've been messing with this on and off for a quite a while now. Finally, instead of trying to fix/modify the TabControl I simply recreated it's functionality. It's actually worked out really well. I made a Tab'like'Control out of a Listbox (Tab headers) and an ItemsControl. The key thing was to set the ItemsPanelTemplate of the ItemsControl to a Grid. A bit of Styling, and a DataTrigger to manage the Visibility of the Items and voila. It works perfect, each "Tab" is a unique object and preserves all it's UI states like scroll position, selections, column widths, etc. Any downsides or problems that might occur with this type of solution?

       <DockPanel>
            <ListBox
                DockPanel.Dock="Top"
                ItemsSource="{Binding Tabs}"
                SelectedItem="{Binding SelectedTab}"
                ItemContainerStyle="{StaticResource ImitateTabControlStyle}">
                <ListBox.ItemsPanel>
                    <ItemsPanelTemplate>
                        <StackPanel
                            Orientation="Horizontal">
                        </StackPanel>
                    </ItemsPanelTemplate>
                </ListBox.ItemsPanel>

                <ListBox.ItemTemplate>
                    <DataTemplate>                            
                        <StackPanel 
                            Margin="2,2,2,0"
                            Orientation="Horizontal" >
                            <TextBlock 
                                Margin="4,0" FontWeight="Bold"
                                Padding="2"
                                VerticalAlignment="Center" HorizontalAlignment="Left"
                                Text="{Binding Name}" >
                            </TextBlock>
                            <Button
                                Margin="4,0"
                                Command="{Binding CloseCommand}">
                                <Image Source="/TERM;component/Images/Symbol-Delete.png" MaxHeight="20"/>
                            </Button>
                        </StackPanel>                            
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
            <ItemsControl    
                ItemsSource="{Binding Tabs}">
                <ItemsControl.ItemsPanel>
                    <ItemsPanelTemplate>
                        <Grid />
                    </ItemsPanelTemplate>
                </ItemsControl.ItemsPanel>
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <ContentControl                                
                            Content="{Binding}">
                            <ContentControl.Style>
                                <Style>
                                    <Style.Triggers>
                                        <DataTrigger
                                            Binding="{Binding IsSelected}" Value="False">
                                            <Setter Property="ContentControl.Visibility" Value="Hidden" />                                                
                                        </DataTrigger>
                                    </Style.Triggers>
                                </Style>
                            </ContentControl.Style>
                        </ContentControl>
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>                
        </DockPanel>