Silverlight 5–Markup Extensions

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原文链接：http://www.cnblogs.com/Ruiyi/archive/2011/12/24/2300353.html

文章标签：

#sketch

本文介绍了 Silverlight 5 中使用的四种自定义标记扩展：StaticExtension、StandardTwoWayBindingExtension、InvokeExtension 和 ResxExtension。这些扩展可以增强 XAML 的功能，使开发者能够更加灵活地处理 UI 绑定和资源调用。

refer:

http://mtaulty.com/CommunityServer/blogs/mike_taultys_blog/archive/2011/04/26/silverlight-5-beta-rough-notes-markup-extensions.aspx

http://www.wintellect.com/CS/blogs/jprosise/archive/2011/04/15/using-custom-markup-extensions-in-silverlight-5.aspx

1. StaticExtension

public class StaticExtension : MarkupExtension
{
public string TypeName { get; set; }
public string PropertyName { get; set; }

public override object ProvideValue(IServiceProvider serviceProvider)
{
object returnValue = null;

// no checking of any return values at all here.
var t = Type.GetType(this.TypeName);

var p = t.GetProperty(this.PropertyName,
BindingFlags.Static | BindingFlags.Public);

var v = p.GetValue(null, null);

    // NB: there's more to do here no doubt than just try for IConvertible on
    // a simple property accessor, this is just a sketch.
    if (v is IConvertible)
    {
      IProvideValueTarget ipvt =
        serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;

      if (ipvt != null)
      {
        PropertyInfo pi = (PropertyInfo)ipvt.TargetProperty;

        returnValue = Convert.ChangeType(v, pi.PropertyType, null);
      }
    }
    else
    {
      returnValue = v;
    }
    return (returnValue);
}
}

Usage 1:

Usage 2:

<Grid x:Name="LayoutRoot">
<Grid.Resources>
    <sys:String
      x:Key="type">System.Windows.Application,System.Windows, Version=5.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e</sys:String>
</Grid.Resources>
<TextBlock
    DataContext="{local:Static TypeName={StaticResource type},PropertyName=Current}"
    Text="{Binding InstallState}" />
</Grid>

2. StandardTwoWayBindingExtension

public class StandardTwoWayBindingExtension : Binding
{
public StandardTwoWayBindingExtension()
{
    this.ValidatesOnNotifyDataErrors = true;
    this.NotifyOnValidationError = true;
    this.Mode = BindingMode.TwoWay;
}
}

Usage:

3. InvokeExtension

public class InvokeExtension : MarkupExtension
{
public string MethodName { get; set; }
public object Source { get; set; }

public override object ProvideValue(IServiceProvider serviceProvider)
{
Delegate returnValue = null;

Type sourceType = this.Source.GetType();

MethodInfo methodInfo = sourceType.GetMethod(this.MethodName,
BindingFlags.Public | BindingFlags.Instance);

IProvideValueTarget ipvt =
serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;

    if (ipvt != null)
    {
      EventInfo targetProperty = ipvt.TargetProperty as EventInfo;

      if (targetProperty != null)
      {
        // This is where we fall over if the types of the event and the
        // handler don't match. We could check IsAssignableFrom and do
        // something other than throw.
        returnValue = Delegate.CreateDelegate(
          targetProperty.EventHandlerType, this.Source, methodInfo);
      }
    }
    return (returnValue);
}
}

Usage:

Or: