Question

如果你自己编写MarkupExtension，你可能偶然发现IServiceProvider serviceProvider - 参数在设计时在运行期间是不同的。例如，您无法获得IRootObjectProvider。那么有关于参数对象实现哪个Interfaces的文档，是否有解决方法来获取根对象？

Answer 1

写了一个小助手，看看哪些服务可用：

public class ServiceExtension : MarkupExtension
{
    public ServiceExtension()
    {
    }

    public ServiceExtension(Type serviceType)
    {
        ServiceType = serviceType;
    }

    [ConstructorArgument("serviceType")]
    public Type ServiceType { get; set; }

    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public object Service { get; set; }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        if (ServiceType == null)
        {
            Service= "ServiceType == null";
            return this;
        }
        var service = serviceProvider.GetService(ServiceType);
        Service= service ?? "null";
        return this;
    }
}

<Style TargetType="{x:Type HeaderedContentControl}">
    <Setter Property="Header" Value="{Binding ServiceType}" />
    <Setter Property="Content" Value="{Binding Service}" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type HeaderedContentControl}">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" SharedSizeGroup="Col1" />
                        <ColumnDefinition />
                    </Grid.ColumnDefinitions>
                    <ContentPresenter Grid.Column="0"
                                      Margin="0,0,5,0"
                                      ContentSource="Header" />
                    <ContentPresenter Grid.Column="1" ContentSource="Content" />
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

<ItemsControl Grid.IsSharedSizeScope="True">
    <HeaderedContentControl DataContext="{local:Service {x:Type xaml:IXamlNameProvider}}" />
    <HeaderedContentControl DataContext="{local:Service {x:Type xaml:IXamlNameResolver}}" />

    <HeaderedContentControl DataContext="{local:Service {x:Type x:IProvideValueTarget}}" />
    <HeaderedContentControl DataContext="{local:Service {x:Type x:IXamlTypeResolver}}" />
    <HeaderedContentControl DataContext="{local:Service {x:Type x:IValueSerializerContext}}" />
    <HeaderedContentControl DataContext="{local:Service {x:Type componentModel:ITypeDescriptorContext}}" />
    <HeaderedContentControl DataContext="{local:Service {x:Type xaml:IDestinationTypeProvider}}" />

    <HeaderedContentControl DataContext="{local:Service {x:Type xaml:IXamlNamespaceResolver}}" />
    <HeaderedContentControl DataContext="{local:Service {x:Type xaml:IXamlSchemaContextProvider}}" />

    <HeaderedContentControl DataContext="{local:Service {x:Type xaml:IRootObjectProvider}}" />
    <HeaderedContentControl DataContext="{local:Service {x:Type x:IUriContext}}" />
    <HeaderedContentControl DataContext="{local:Service {x:Type xaml:IAmbientProvider}}" />
</ItemsControl>

Answer 2

请查看以下链接将为您提供帮助

http://msdn.microsoft.com/en-us/library/system.windows.markup.markupextension.providevalue.aspx

http://vimalck.wordpress.com/2013/06/22/markup-extensions-for-events-in-net-4-5-2/

设计时的MarkupExtension.ProvideValue（IServiceProvider serviceProvider）

2 个答案: