If you have more than one AxDataSource control in one user control , make sure you mark the Role property of  all but one AxDataSource controls to anything other than “Provider” or “ProviderConsumer”. Otherwise you will get an error.

 In one usercontrol , only one AxDataSource control could provide the context to other controls and web parts. So only one can have the provider role.

By default the Role Property of the AxDataSource control is set to "ProviderConsumer" .  So if you have more than one control with the default set of properties. you will get Specified method is not supported error. To fix this change the role to None or Consumer.