Why is The C# code not returning a value from Stored Procedure

Question

I am trying to pull one piece of data from my database using a Stored Procedure that looks like this.

USE [PSD]
GO
/****** Object:  StoredProcedure [dbo].[ocso_GetNextDTEventNumber]    Script Date: 1/19/2017 10:12:19 AM ******/
SET ANSI_NULLS ON
GO
  SET QUOTED_IDENTIFIER ON
GO

ALTER PROCEDURE [dbo].[ocso_GetNextDTEventNumber] 
    @EventNumber varchar(15) OUTPUT
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

--increment last number by 1
UPDATE LU_EVENT_NUMBERS SET evn_last_number = evn_last_number + 1 where evn_year = Year(GetDate())
--return event number to caller

    --Get the next event number for all incidents
SELECT @EventNumber = evn_comp_formatted_next_num from LU_EVENT_NUMBERS where evn_year = Year(GetDate())

END

I test this procedure using this SQL Code

DECLARE @NewEventNumber varchar(15)
Execute dbo.ocso_GetNextDTEventNumber
@EventNumber = @NewEventNumber OUTPUT;
Print convert(varchar(15),@NewEventNumber)

And I get the results I would expect. Now when I try to get the results in my C# code which looks like this:

public string GetEventNumber(string enumber)
        {
            string results;

            SqlConnection _con = new SqlConnection();
            _con.ConnectionString =
                "Data Source=ops-devsql;" +
                "Initial Catalog=PSD;" +
                "User id=****;" +
                "Password=****;";
            _con.Open();

            {
                using (SqlCommand _cmd = new SqlCommand("ocso_GetNextDTEventNumber", _con))
                {
                    _cmd.Parameters.Add("@NewEventNumber", SqlDbType.VarChar, 15)
                                   .Direction = ParameterDirection.Output;
                    _cmd.ExecuteNonQuery();

                    results = _cmd.Parameters["@NewEventNumber"].Value.ToString();
                   //results = (string)_cmd.Parameters["@NewEventNumber"].Value.ToString();
                    return results;
                }
            }
        }

I get an empty string back. Why is this not working?

Answer 1

You have forgotten to tell the command that you want to execute a stored-procedure:

using (SqlCommand _cmd = new SqlCommand("ocso_GetNextDTEventNumber", _con))
{
   _cmd.CommandType = CommandType.StoredProcedure;
   //...
}

If you don't specify it the default is taken which is Text (so a plain sql query). I guess you have somewhere an empty Try....Catch because this should cause an exception.

You should also use the same parameter name:

_cmd.Parameters.Add("@EventNumber", SqlDbType.VarChar, 15).Direction = ParameterDirection.Output;
_cmd.ExecuteNonQuery();
results = _cmd.Parameters["@EventNumber"].Value.ToString();