The supported data types currently are found on MSDN - http://msdn.microsoft.com/en-us/library/windowsazure/dd179338.aspx. As you've seen ulong isn't one of them.
However, you can get around this by dealing with serialization/deserialization on your own. If you are using the 2.0 or greater Storage library you can use the ITableEntity interface on your object, override the ReadEntity
and WriteEntity
methods.