Change Data template dynamically

Question

I have a item control which is bound to Tasks. Each task has task state. I have defined different data templates for each task state, and also data template selector.

Problem is that I am not able to figure out how to trigger data template selector when task state is changed dynamically.

I want to know how to use data triggers together with data templates.

If this will not work out, i will explore other alternatives such as
1. Attached Property bound to task state. Any change will dynamically set data template.
2. Visual State Manager

Elaboration

maybe this answer will fit also for you #8715815 – Regret

Looked at this answer already. This may work, but looks a bit complex. Looking for simpler solution. – Elaboration

The question maybe duplicated with how-to-trigger-datatemplateselector-when-property-changes and ControlTemplate with DataTrigger Vs. DataTemplate with DataTemplateSelector – Januarius

Answer 1

A DataTemplateSelector does not respond to PropertyChange notifications, so it doesn't get re-evaluated when your properties change.

The alternative I use is DataTriggers that changes the Template based on a property.

For example, this will draw all TaskModel objects using a ContentControl, and the ContentControl.Template is based on the TaskStatus property of the TaskModel

<DataTemplate x:Key="OpenTaskTemplate" TargetType="{x:Type local:TaskModel}">
     <TextBlock Text="I'm an Open Task" />
</DataTemplate> 

<DataTemplate x:Key="ClosedTaskTemplate" TargetType="{x:Type local:TaskModel}">
     <TextBlock Text="I'm a Closed Task" />
 </DataTemplate>

<DataTemplate DataType="{x:Type local:TaskModel}">
     <ContentControl Content="{Binding }">
         <ContentControl.Style>
             <Style TargetType="{x:Type ContentControl}">

                 <!-- Default Template -->
                 <Setter Property="ContentTemplate" Value="{StaticResource OpenTaskTemplate}" />

                 <!-- Triggers to change Template -->
                 <Style.Triggers>
                     <DataTrigger Binding="{Binding TaskStatus}" Value="Closed">
                         <Setter Property="ContentTemplate" Value="{StaticResource ClosedTaskTemplate}" />
                     </DataTrigger>
                 </Style.Triggers>
             </Style>
         </ContentControl.Style>
     </ContentControl>
 </DataTemplate>

Loafer

hmm, DataTemplate doesn't seem have a targetType member. Am I missing something? – Rosario

@JakeGaston Are you using Silverlight? I don't think implicit DataTemplates (ones with only TargetType set) are implemented in Silverlight until 4.5. – Loafer

Answer 2

Just a quick note for anyone that found this incredibly helpful as I did -

Currently with WPF, it looks like you'll want to use DataType rather than TargetType on your DataTemplate definitions:

<DataTemplate x:Key="OpenTaskTemplate" DataType="{x:Type local:TaskModel}">
     <TextBlock Text="I'm an Open Task" />
</DataTemplate> 

<DataTemplate x:Key="ClosedTaskTemplate" DataType="{x:Type local:TaskModel}">
     <TextBlock Text="I'm a Closed Task" />
 </DataTemplate>

Ipomoea