silverlight 中怎么实现浏览器百分比 放大缩小页面的效果

/// <summary>    /// 浏览器屏幕信息类    /// </summary>    public class Browser    {        /// <summary>          /// During static instantiation, only the Netscape flag is checked          /// </summary>          static Browser()        {            _isNavigator = HtmlPage.BrowserInformation.Name.Contains("Netscape");        }        /// <summary>          /// Flag indicating Navigator/Firefox/Safari or Internet Explorer          /// </summary>          private static bool _isNavigator;        /// <summary>          /// Provides quick access to the window.screen ScriptObject          /// </summary>          private static ScriptObject Screen        {            get            {                ScriptObject screen = (ScriptObject)HtmlPage.Window.GetProperty("screen");                if (screen == null)                {                    throw new InvalidOperationException();                }                return screen;            }        }        /// <summary>          /// Gets the window object's client width          /// </summary>          public static double ClientWidth        {            get            {                return _isNavigator ? (double)HtmlPage.Window.GetProperty("innerWidth")                    : (double)HtmlPage.Document.Body.GetProperty("clientWidth");            }        }        /// <summary>          /// Gets the window object's client height          /// </summary>          public static double ClientHeight        {            get            {                return _isNavigator ? (double)HtmlPage.Window.GetProperty("innerHeight")                    : (double)HtmlPage.Document.Body.GetProperty("clientHeight");            }        }        /// <summary>          /// Gets the current horizontal scrolling offset          /// </summary>          public static double ScrollLeft        {            get            {                return _isNavigator ? (double)HtmlPage.Window.GetProperty("pageXOffset")                    : (double)HtmlPage.Document.Body.GetProperty("scrollLeft");            }        }        /// <summary>          /// Gets the current vertical scrolling offset          /// </summary>          public static double ScrollTop        {            get            {                return _isNavigator ? (double)HtmlPage.Window.GetProperty("pageYOffset")                    : (double)HtmlPage.Document.Body.GetProperty("scrollHeight");            }        }        /// <summary>          /// Gets the width of the entire display          /// </summary>          public static double ScreenWidth        {            get            {                return (double)Screen.GetProperty("width");            }        }        /// <summary>          /// Gets the height of the entire display          /// </summary>          public static double ScreenHeight        {            get            {                return (double)Screen.GetProperty("height");            }        }        /// <summary>          /// Gets the width of the available screen real estate, excluding the dock          /// or task bar          /// </summary>          public static double AvailableScreenWidth        {            get            {                return (double)Screen.GetProperty("availWidth");            }        }        /// <summary>          /// Gets the height of the available screen real estate, excluding the dock /// or task bar          /// </summary>          public static double AvailableScreenHeight        {            get            {                return (double)Screen.GetProperty("availHeight");            }        }        /// <summary>          /// Gets the absolute left pixel position of the window in display coordinates          /// </summary>          public static double ScreenPositionLeft        {            get            {                return _isNavigator ? (double)HtmlPage.Window.GetProperty("screenX")                    : (double)HtmlPage.Window.GetProperty("screenLeft");            }        }        /// <summary>          /// Gets the absolute top pixel position of the window in display coordinates          /// </summary>          public static double ScreenPositionTop        {            get            {                return _isNavigator ? (double)HtmlPage.Window.GetProperty("screenY")                    : (double)HtmlPage.Window.GetProperty("screenTop");            }        }    }