//读取的是需要返回值的，括号内基本就是附加对象public static string GetHtmlString(DependencyObject D)//赋值不需要返回值，括号内参数需要两个一个附加对象，一个添加的值      public static void SetHtmlString(DependencyObject D, string HtmlString)

  //注册一个名为setHtmlString的附加属性，利用其.RegisterAttached方法，括号内参数分别是，要添加的属性，属性的类型，属性的所有者，以及元数据实例，且其中包含返回public static readonly DependencyProperty setHtmlString =DependencyProperty.RegisterAttached("HtmlString", typeof(string), typeof(MainPage), new PropertyMetadata(null, CallBack));
//自动注册名为CallBack 的方法，private static void CallBack(DependencyObject d, DependencyPropertyChangedEventArgs e){        throw new NotImplementedException();           }

   class GetWebHtml{//注册一个附加属性，括号内的参数，分别是 要添加的附加属性的名字，附加属性的类型，附加属性的所有者，附加属性的元数据，并且创建一个返回public static readonly DependencyProperty setHtmlString =DependencyProperty.RegisterAttached("HtmlString",typeof(string),typeof(GetWebHtml),new PropertyMetadata(null, CallBack));//这里对你要控件的操作private static void CallBack(DependencyObject d, DependencyPropertyChangedEventArgs e){       //将附加对象进行强制转换WebView setData = d as WebView;//添加值
                setData.NavigateToString(e.NewValue.ToString());                    }//读取静态方法public static string GetHtmlString(DependencyObject D){return (string)D.GetValue(setHtmlString);}// 赋值静态方法public static void SetHtmlString(DependencyObject D, string HtmlString){D.SetValue(setHtmlString, HtmlString);}}

 <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">        <ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">

<WebView  local:GetWebHtml.HtmlString="{Binding T}" x:Name="_webview" />

        </ScrollViewer></Grid>

  public sealed partial class MainPage : Page{public class Data{public string T { get; set; }}public MainPage(){this.InitializeComponent();           Data _data = new Data();            string data ="<img src=\"https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1487774858602&di=bc76e28a0328dd7a4412c28ac96c844d&imgtype=0&src=http%3A%2F%2Fi-7.vcimg.com%2Fcrop%2F32eb472901ee07279ce5cbf8810ea493467409%2528600x%2529%2Fthumb.jpg\"/>";_data.T = data;this.DataContext = _data;}}