I just want to understand the following scenario. Where I am implementing a <TabControl>
bound to a ObservableCollection<TabViewModel>
No Data Templates
When I don't have any DataTemplate
s, the text WpfApplication1.TabViewModel
appears in the Tab Header and Content. Ok I understand this part.
Just ItemTemplate
When I just have
<TabControl.ItemTemplate> <DataTemplate> <StackPanel Orientation="Horizontal"> <TextBlock Text="{Binding TabTitle}" /> </StackPanel> </DataTemplate> </TabControl.ItemTemplate>
Then my tab header is filled. The tab content is still WpfApplication1.TabViewModel
.
Just DataTemplate
When I just have the below in my <Window.Resources>
<DataTemplate DataType="{x:Type local:TabViewModel}"> <TextBox Text="{Binding Text}" /> </DataTemplate>
That templates fills up the tab header.
Both
When I have both, the ItemTemplate
fills up the Tab Header while the DataTemplate
fills up the tab content. Why all this difference. ItemTemplate
& DataTemplate
fills up the tab header if the other is not present. If both are present, ItemTemplate
fills up the header while DataTemplate
fills the content.
Though I have things working, I am quite confused. Shouldn't something like <TabControl.HeaderTemplate>
be what fills the header and <TabControl.ItemTemplate>
fill up the content?
Windows TabControl is a useful control that allows you display multiple dialogs tabs on a single form by switching between the tabs. A tab acts as another Form that can host other controls. Figure 1 shows an example of TabControl in Visual Studio . NET, which allows you to switch among multiple files using the tabs.
A StackPanel allows you to stack elements in a specified direction. By using properties that are defined on StackPanel, content can flow both vertically, which is the default setting, or horizontally.
WPF TabControl provides two templates property for changing the UI for Header and Content area. ItemTemplate - Get/Set DataTemplate for TabItem Header. ContentTemplate - Get/Set DateTemplate for TabItem Content.
Windows Presentation Foundation (WPF) supports browser-style navigation that can be used in two types of applications: standalone applications and XAML browser applications (XBAPs). To package content for navigation, WPF provides the Page class.
First of all, there are two templates involved here:
TabControl.ItemTemplate
, used to render the TabItem
headersTabControl.ContentTemplate
, used to render the TabItem
contentsIf you don't set these properties explicitly then WPF will attempt to resolve them elsewhere. It will walk up the logical tree looking for a resource telling it how to render your view model. If it finds a DataTemplate
that has a matching DataType
but no key, it will use it to render the view model. If it doesn't find one, it'll default to rendering the ToString
value of the object.
So, if you want to be explicit, you want something like this:
<TabControl ItemsSource="{Binding Tabs}"> <TabControl.ItemTemplate> <DataTemplate> <TextBlock Text="{Binding TabTitle}"/> </DataTemplate> </TabControl.ItemTemplate> <TabControl.ContentTemplate> <DataTemplate> <TextBlock Text="{Binding Text}"/> </DataTemplate> </TabControl.ContentTemplate> </TabControl>
Since you're not being specific, WPF is attempting to walk up your logical tree to find an appropriate DataTemplate
. When it finds it, it uses it to render the view model. Where it doesn't find it, it calls ToString
and renders that.
So to address your specific cases:
Just ItemTemplate
You've explicitly stated how to render tab headers but not tab contents. So the former is rendered using the provided DataTemplate
, but the latter will default to ToString
.
Just DataTemplate
You've not explicitly stated how to render either tab headers or tab contents. Therefore, WPF searches for an appropriate DataTemplate
for both. Since both contain an instance of your view model (that's their DataContext
) then the same DataTemplate
will be used to render tab headers and their contents.
NOTE: you didn't explicitly state that this is what's happening in your question. Correct me if I'm wrong.
Both
In this case, you've explicitly stated how to render tab headers but not tab contents. Therefore, the explicit DataTemplate
is used for tab headers and the implicit DataTemplate
is used for tab contents.
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