[OperationContract(AsyncPattern = true, Action = "http://schemas.microsoft.com/sqlserver/2005/06/30/reporting/reportingservices/GetDataSourceContents", ReplyAction = "*")]
IAsyncResult BeginGetDataSourceContents(GetDataSourceContentsRequest request, AsyncCallback callback, object asyncState)

<OperationContract(AsyncPattern:=True, Action:="http://schemas.microsoft.com/sqlserver/2005/06/30/reporting/reportingservices/GetDataSourceContents", ReplyAction:="*")>
Function BeginGetDataSourceContents(request As GetDataSourceContentsRequest, callback As AsyncCallback, asyncState As Object) As IAsyncResult