SqlException.Message duplicated when calling sqlserver stored proc

Question

I have a stored procedure that gives a friendly enough error that I want to show to the users but when I call it from .net it comes out twice. When I call the proc from sql server management studio it only comes out once.

Here is a cutdown version of the stored proc:

ALTER PROC [Production].[spDoSomething] (
            @PassedID int)
AS
BEGIN
    DECLARE @ErrorString nvarchar(500);
    BEGIN TRY
        ...
        RAISERROR('Bad things are happening.', 11 /*severity*/, 1 /*state*/);
        ...
    END TRY
    BEGIN CATCH
        SET @ErrorString = 'Error found:' + ERROR_MESSAGE();
        PRINT @ErrorString;
        RAISERROR(@ErrorString, 11 /*severity*/, 1 /*state*/);
    END CATCH
END

I call this in some c# code using ExecuteNonQuery() of a System.Data.SqlClient.SQLCommand object then I catch a System.Data.SqlClient.SQLException but the Message contains

"Error: Found Bad things are happening.\nError Found: Bad things are happening."

Does anyone know a reason why it comes out twice?

This is on sql server 2008 and .net 3.5

Answer 1

Please comment the "PRINT @ErrorString;" statement. When SQL Engine throws an error, it would displays all the messages are available in the message stack.

Reason:

Try to run below code snap.

CREATE PROCEDURE ErrorHandler

AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

   DECLARE @ErrorString nvarchar(500);
    BEGIN TRY
        RAISERROR('Bad things are happening.', 11 /*severity*/, 1 /*state*/);
    END TRY
    BEGIN CATCH
        SET @ErrorString = 'Error found:' + ERROR_MESSAGE();
        PRINT @ErrorString;
        PRINT 'Stack overflow'
        RAISERROR(@ErrorString, 11 /*severity*/, 1 /*state*/);
    END CATCH
END
GO

EXEC ErrorHandler

SQL engine generates 3 messages;

1. 1st for PRINT @ErrorString;

2. 2nd for PRINT 'Stack overflow'

3. 3rd for RAISERROR(@ErrorString, 11 /*severity*/, 1 /*state*/);