Provides a way to choose a DataTemplate based on the data object and the data-bound element.
Assembly: PresentationFramework (in PresentationFramework.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation
Thetype exposes the following members.
|Equals(Object)||Determines whether the specified object is equal to the current object. (Inherited from Object.)|
|Finalize||Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)|
|GetHashCode||Serves as the default hash function. (Inherited from Object.)|
|GetType||Gets the Type of the current instance. (Inherited from Object.)|
|MemberwiseClone||Creates a shallow copy of the current Object. (Inherited from Object.)|
|SelectTemplate||When overridden in a derived class, returns a DataTemplate based on custom logic.|
|ToString||Returns a string that represents the current object. (Inherited from Object.)|
Typically, you create a when you have more than one DataTemplate for the same type of objects and you want to supply your own logic to choose a DataTemplate to apply based on the properties of each data object. Note that if you have objects of different types you can set the DataType property on the DataTemplate. If you do that then there is no need to create a . Furthermore, if you have objects of the same type but with different properties, you can also consider using a DataTrigger or a data converter. For more information, see Data Templating Overview.
To create a template selector, create a class that inherits from and override the SelectTemplate method. Once your class is defined you can assign an instance of the class to the template selector property of your element.
In this example, the binding source is a list of Task objects. One of the properties of a Task object is Priority. There are two data templates defined, myTaskTemplate and importantTaskTemplate.
To supply logic to choose which DataTemplate to use based on the Priority value of the data object, create a subclass of and override the SelectTemplate method. In the following example, the SelectTemplate method provides logic to return the appropriate template based on the value of the Priority property. The template to return is found in the resources of the enveloping Window element.
Namespace SDKSample Public Class TaskListDataTemplateSelector Inherits DataTemplateSelector Public Overrides Function SelectTemplate(ByVal item As Object, ByVal container As DependencyObject) As DataTemplate Dim element As FrameworkElement element = TryCast(container, FrameworkElement) If element IsNot Nothing AndAlso item IsNot Nothing AndAlso TypeOf item Is Task Then Dim taskitem As Task = TryCast(item, Task) If taskitem.Priority = 1 Then Return TryCast(element.FindResource("importantTaskTemplate"), DataTemplate) Else Return TryCast(element.FindResource("myTaskTemplate"), DataTemplate) End If End If Return Nothing End Function End Class End Namespace
We can then declare the TaskListDataTemplateSelector as a resource:
To use the template selector resource, assign it to the ItemTemplateSelector property of the ListBox. The ListBox calls the SelectTemplate method of the TaskListDataTemplateSelector for each of the items in the underlying collection. The call passes the data object as the item parameter. The DataTemplate that is returned by the method is then applied to that data object.
For the complete sample, see Introduction to Data Templating Sample.