C# WP8.1中的XamlReader错误

我从MSDN复制了这个代码

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请帮我修一下。谢谢

请尝试以下XAML，似乎缺少xmlns

string xaml = "<Ellipse Name=\"EllipseAdded\" Width=\"300.5\" Height=\"200\" Fill=\"Red\"       xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\"/>";

string xaml=”“；

The text associated with this error code could not be found. illegal 
qualified name character [Line: 1 Position: 68]

string xaml = "<Ellipse Name=\"EllipseAdded\" Width=\"300.5\" Height=\"200\" Fill=\"Red\"       xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\"/>";