Working in the cloud, living on the west coast, and other things that are me.http://blogs.msdn.com/mark/atom.xmlCommunity Server2008-11-18T08:58:00Zhttp://blogs.msdn.com/mark/archive/2008/11/18/anonymous-types-and-silverlight-databinding.aspx2008-11-18T19:58:00Z2008-11-18T19:58:00Z<P>My journey through working in the web world has taken me many places in the past: Cold Fusion, PHP, Classic ASP all the way to the latest version of <A target=_blank href="http://www.silverlight.net/" mce_href="http://www.silverlight.net">Silverlight</A>.&nbsp; I'll post some of the small things I come across as I'm learning this new technology in part to document my learning process but hopefully more to help out anyone else who runs into the same issues.&nbsp; My first victim, this exception:</P><CODE> <P mce_keep="true">An unhandled exception 'Unhandled Error in Silverlight 2 Application Code: 4004 Category ManagedRuntimeError Message: System.MethodAccessException: &lt;&gt;f__AnonymousType0`.get_Summary()</P></CODE> <P mce_keep="true">I ran into this while&nbsp;writing a quick prototype trying learning all the pieces of silverlight.&nbsp; My first app was an xml feed reader with code similar to this:</P><CODE> <P mce_keep="true">[get xml feed content into and XDocument called feed]</P> <P mce_keep="true">CustomFeedItemControl.FeedItem&nbsp;= from item in feed.Element("item") select new { Title = item.Element("title").Value, Summary = item.Element("description").Value };</P></CODE> <P mce_keep="true">The first thing that comes up on searches is information on the <A target=_blank href="http://blogs.msdn.com/shawnfa/archive/2007/05/09/the-silverlight-security-model.aspx" mce_href="http://blogs.msdn.com/shawnfa/archive/2007/05/09/the-silverlight-security-model.aspx">Silverlight security model</A>.&nbsp; Any calls made from security transparent code to critical code will throw a MethodAcessException.&nbsp; The second clue here is the "get_Summary()" part of the exception.&nbsp; Remember that in C# properties are really just syntactic sugar for accessor/modifier methods for a field and internally the get_ and set_ methods are created for interoperability with other .Net languages.&nbsp; So basically, there's a security exception trying to access the property on the anonymous typed class.&nbsp; But why?</P> <P mce_keep="true">Well this occurs because anonymous objects are typed as internal.&nbsp; Silverlight will not reflect on private members as part of its security model and throws this exception.&nbsp; One solution for my example is to create some kind of public type "FeedItem" with properties Title, Summary, etc.&nbsp; In my next post I'll talk about a better solution for dealing with feeds altogether.</P><img src="http://blogs.msdn.com/aggbug.aspx?PostID=9119341" width="1" height="1">mdefalcohttp://blogs.msdn.com/members/mdefalco.aspx