Question

Why the error does not appear at the UI layer? I am using ExecuteScaler

BEGIN CATCH

  PRINT N'The transaction is in an uncommittable state. Rolling back transaction.'
  ROLLBACK TRANSACTION;

  DECLARE @ErrorMessage NVARCHAR(4000);
  DECLARE @ErrorSeverity INT;
  DECLARE @ErrorState INT;

  SELECT @ErrorMessage = ERROR_MESSAGE(),
         @ErrorSeverity = ERROR_SEVERITY(),
         @ErrorState = ERROR_STATE();

  RAISERROR (@ErrorMessage, 
             @ErrorSeverity,
             @ErrorState);

END CATCH

Thanks

Answer 1

You can only raise user messages, system messages can only be raised by the engine:

Error numbers for user-defined error
messages should be greater than 50000.
When msg_id is not specified,
RAISERROR raises an error message with
an error number of 50000.

Therefore you cannot raise the original @ErrorMessage, you have to raise a new error code.

Also, your catch block is incorrect in as it assumes an uncommittable transaction. This is not always the case, you must check the result of XACT_STATE() before deciding if the transaction is doomed. There are many cases on which the error handling can continue the transaction. See Exception handling and nested transactions.