This error was thrown at Attunity.Data.AisClient.AisCommand.ExecuteReader and it means that the data type whose ID is 51 is not supported by the ADO.NET provider.

Looking up code 51 in the dbtypeid.h file (found in the include directory of the AIS server kit) shows this is DT_TYPE_FILLER_.

The problem is that a certain field was defined with type FILLER and then the SELECT * FROM TBL retrieved it resulting in the error message.

To work around this problem, set the explicitSelect attribute of the field to 'true' in the ADD definition of the table. Setting this attribute means that a field will not be returned in SELECT * - only if it is explicitly requested.

Recent versions of AIS automatically set the explicitSelect attribute of FILLER fields to avoid this issue.