[WPF] DataTemplate Binding to Interface
在WPF内可以使用DataTemplate，来辅助完成对对象集合做DataBinding的工作。并且透过DataTemplate的DataType属性，来让对象集合中不同的对象，经过DataBinding之后能有「不同的外观」。简单的范例如下：不同的车辆类型，会依照车辆类型，呈现不同的详细数据。
namespace BindingInterfaceSample
{
public class Car
{
public string Name { get; set; }
}
public class Truck : Car
{
public int MaxLoad { get; set; }
}
public class Roadster : Car
{
public int MaxSpeed { get; set; }
}
}
<Window x:Class="BindingInterfaceSample.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:clk="clr-namespace:BindingInterfaceSample"
Title="MainWindow" Height="350" Width="525">
<ItemsControl >
<ItemsControl.Items>
<clk:Truck Name="Truck01" MaxLoad="100" />
<clk:Truck Name="Truck02" MaxLoad="500" />
<clk:Roadster Name="Roadster01" MaxSpeed="99" />
</ItemsControl.Items>
<ItemsControl.Resources>
<DataTemplate DataType="{x:Type clk:Truck}">
<WrapPanel>
<TextBlock Text="Truck" />
<TextBlock Text="{Binding Path=MaxLoad}" />
</WrapPanel>
</DataTemplate>
<DataTemplate DataType="{x:Type clk:Roadster}">
<WrapPanel>
<TextBlock Text="Roadster" />
<TextBlock Text="{Binding Path=MaxSpeed}" />
</WrapPanel>
</DataTemplate>
</ItemsControl.Resources>
</ItemsControl>
</Window>
![[WPF] DataTemplate Binding to Interface](http://Files.Dotblogs.com.tw/clark/1205/201252919522525.png)
反过来说，也可以经由DataTemplate的DataType属性，来让对象集合中不同的对象，经过DataBinding之后能有「相同的外观」。简单的范例如下：只要是车，都只呈现车的数据。
namespace BindingInterfaceSample
{
public class Car
{
public string Name { get; set; }
}
public class Truck : Car
{
public int MaxLoad { get; set; }
}
public class Roadster : Car
{
public int MaxSpeed { get; set; }
}
}
<Window x:Class="BindingInterfaceSample.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:clk="clr-namespace:BindingInterfaceSample"
Title="MainWindow" Height="350" Width="525">
<ItemsControl >
<ItemsControl.Items>
<clk:Truck Name="Truck01" MaxLoad="100" />
<clk:Truck Name="Truck02" MaxLoad="500" />
<clk:Roadster Name="Roadster01" MaxSpeed="99" />
</ItemsControl.Items>
<ItemsControl.Resources>
<DataTemplate DataType="{x:Type clk:Car}">
<Button Content="{Binding Path=Name}" />
</DataTemplate>
</ItemsControl.Resources>
</ItemsControl>
</Window>
![[WPF] DataTemplate Binding to Interface](http://Files.Dotblogs.com.tw/clark/1205/2012529195332.png)
而在让对象集合中不同的对象，经过DataBinding之后能有「相同的外观」。这个使用情景中，DataTemplate的DataType如果设定为Interface型别，在WPF中会出现意外的执行结果。简单的范例如下：DataType设定为Interface型别，会无法对应DataTemplate。
namespace BindingInterfaceSample
{
public interface ICar
{
string Name { get; set; }
}
public class Truck : ICar
{
public string Name { get; set; }
public int MaxLoad { get; set; }
}
public class Roadster : ICar
{
public string Name { get; set; }
public int MaxSpeed { get; set; }
}
}
<Window x:Class="BindingInterfaceSample.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:clk="clr-namespace:BindingInterfaceSample"
Title="MainWindow" Height="350" Width="525">
<ItemsControl >
<ItemsControl.Items>
<clk:Truck Name="Truck01" MaxLoad="100" />
<clk:Truck Name="Truck02" MaxLoad="500" />
<clk:Roadster Name="Roadster01" MaxSpeed="99" />
</ItemsControl.Items>
<ItemsControl.Resources>
<DataTemplate DataType="{x:Type clk:ICar}">
<Button Content="{Binding Path=Name}" />
</DataTemplate>
</ItemsControl.Resources>
</ItemsControl>
</Window>
![[WPF] DataTemplate Binding to Interface](http://Files.Dotblogs.com.tw/clark/1205/2012529195330833.png)
遇到必须设定DataTemplate的DataType为Interface型别的情景。解决的方法很简单：只要改写数据系结容器使用的DataTemplateSelector，增加以Interface型别做索引，查询Resource里的DataTemplate，再用这个DataTemplate来做DataBinding。简单的范例如下：只要是有实做车接口，都只呈现车的数据。
namespace BindingInterfaceSample
{
public interface ICar
{
string Name { get; set; }
}
public class Truck : ICar
{
public string Name { get; set; }
public int MaxLoad { get; set; }
}
public class Roadster : ICar
{
public string Name { get; set; }
public int MaxSpeed { get; set; }
}
}
<Window x:Class="BindingInterfaceSample.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:clk="clr-namespace:BindingInterfaceSample"
Title="MainWindow" Height="350" Width="525">
<ItemsControl>
<ItemsControl.Items>
<clk:Truck Name="Truck01" MaxLoad="100" />
<clk:Truck Name="Truck02" MaxLoad="500" />
<clk:Roadster Name="Roadster01" MaxSpeed="99" />
</ItemsControl.Items>
<ItemsControl.Resources>
<DataTemplate DataType="{x:Type clk:ICar}">
<Button Content="{Binding Path=Name}" />
</DataTemplate>
</ItemsControl.Resources>
<ItemsControl.ItemTemplateSelector>
<clk:StandardDataTemplateSelector />
</ItemsControl.ItemTemplateSelector>
</ItemsControl>
</Window>
namespace BindingInterfaceSample
{
public class StandardDataTemplateSelector : DataTemplateSelector
{
// Methods
public override DataTemplate SelectTemplate(object item, DependencyObject container)
{
#region Require
if (item == null) throw new ArgumentNullException();
if (container == null) throw new ArgumentNullException();
#endregion
// Result
DataTemplate itemDataTemplate = null;
// Base DataTemplate
itemDataTemplate = base.SelectTemplate(item, container);
if (itemDataTemplate != null) return itemDataTemplate;
// Interface DataTemplate
FrameworkElement itemContainer = container as FrameworkElement;
if (itemContainer == null) return null;
foreach (Type itemInterface in item.GetType().GetInterfaces())
{
itemDataTemplate = itemContainer.TryFindResource(new DataTemplateKey(itemInterface)) as DataTemplate;
if (itemDataTemplate != null) break;
}
// Return
return itemDataTemplate;
}
}
}
![[WPF] DataTemplate Binding to Interface](http://Files.Dotblogs.com.tw/clark/1205/2012529195352541.png)
参考数据
Style、DataTemplate 和隐含索引键
DataTemplateKey 类别
范列下载
BindingInterfaceSample点此下载