according to msdn, this doesn't apply to this function.

http://msdn.microsoft.com/en-us/library/windowsazure/hh452241

The Insert Or Merge Entity operation uses the MERGE verb and must be called using the 2011-08-18 version or newer. In addition, it does not use the If-Match header. These attributes distinguish this operation from the Update Entity operation, though the request body is the same for both operations.