如何使用ItemTemplateSelector

WPF 的 ItemsControl 数据绑定中，有时会遇到绑定的数据源是多种类型，并且需要对不同类型使用不同的模板。这个时候就需要用到 ItemTemplateSelector。

ItemTemplateSelector 的定义

ItemTemplateSelector 是 DataTemplateSelector 类型，通常需要定义一个类继承 DataTemplateSelector。

注意，下面代码关键之处在于定义了 DataTemplate 类型的属性，并在 XAML 中设置其值，避免寻找资源。

public class ValueEditorTemplateSelector : DataTemplateSelector
{
	public DataTemplate StandardTemplate
	{
		get { return this.standardTemplate; }
		set { this.standardTemplate = value; }
	}

	public DataTemplate EnumTemplate
	{
		get { return this.enumTemplate; }
		set { this.enumTemplate = value; }
	}

	public override DataTemplate SelectTemplate(object item, DependencyObject container)
	{
		PropertyInformation property = (PropertyInformation)item;

		if (property.PropertyType.IsEnum)
			return EnumTemplate;
		return StandardTemplate;
	}
}

ItemTemplateSelector 的使用

<my:ValueEditorTemplateSelector x:Key="EditorSelector">
    <my:ValueEditorTemplateSelector.StandardTemplate>
        <DataTemplate>
            <DockPanel>
                <editors:MouseWheelValueEditor/>
                <my:StandardValueEditor
                    PropertyType="{Binding PropertyType}"
                    Value="{Binding Value, Mode=TwoWay}"
                    DescriptiveValue="{Binding DescriptiveValue, Mode=OneWay}"
                    IsSelected="{Binding IsSelected, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListViewItem}}}"
                    IsEditable="{Binding CanEdit}"
                    PropertyInfo="{Binding}"/>
                <Border/>
            </DockPanel>
        </DataTemplate>
    </my:ValueEditorTemplateSelector.StandardTemplate>

    <my:ValueEditorTemplateSelector.EnumTemplate>
        <DataTemplate>
            <DockPanel>
                <editors:MouseWheelValueEditor/>
                <my:EnumValueEditor
                    PropertyType="{Binding PropertyType}"
                    Value="{Binding Value, Mode=TwoWay}"
                    DescriptiveValue="{Binding DescriptiveValue, Mode=OneWay}"
                    IsSelected="{Binding IsSelected, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListViewItem}}}"
                    IsEditable="{Binding CanEdit}"
                    PropertyInfo="{Binding}"/>
                <Border/>
            </DockPanel>
        </DataTemplate>
    </my:ValueEditorTemplateSelector.EnumTemplate>
</my:ValueEditorTemplateSelector>