Silverlight2 No Message Class CreateBufferedCopy Method

I am trying to read the answer to soap twice and I got the error already read ... There are some examples of how to avoid this BUT ... they use the CreateBufferedCopy method and I cannot find it on the Silverlight2 object:

Microsoft also has this suggestion in the silverlight doc:

http://msdn.microsoft.com/en-us/library/system.servicemodel.channels.message.getreaderatbodycontents(VS.95).aspx "If you want to access the body multiple times, use CreateBufferedCopy (Int32) to create a MessageBuffer instance. "