Calling stored procedure with return value

Question

I am trying to call a stored procedure from my C# windows application. The stored procedure is running on a local instance of SQL Server 2008. I am able to call the stored procedure but I am not able to retrieve the value back from the stored procedure. This stored procedure is supposed to return the next number in the sequence. I have done research online and all the sites I've seen have pointed to this solution working.

Stored procedure code:

ALTER procedure [dbo].[usp_GetNewSeqVal]
      @SeqName nvarchar(255)
as
begin
      declare @NewSeqVal int
      set NOCOUNT ON
      update AllSequences
      set @NewSeqVal = CurrVal = CurrVal+Incr
      where SeqName = @SeqName

      if @@rowcount = 0 begin
print 'Sequence does not exist'
            return
      end

      return @NewSeqVal
end

Code calling the stored procedure:

SqlConnection conn = new SqlConnection(getConnectionString());
conn.Open();

SqlCommand cmd = new SqlCommand(parameterStatement.getQuery(), conn);
cmd.CommandType = CommandType.StoredProcedure;

SqlParameter param = new SqlParameter();

param = cmd.Parameters.Add("@SeqName", SqlDbType.NVarChar);
param.Direction = ParameterDirection.Input;
param.Value = "SeqName";

SqlDataReader reader = cmd.ExecuteReader();

I have also tried using a DataSet to retrieve the return value with the same result. What am I missing to get the return value from my stored procedure? If more information is needed, please let me know.

Answer 1

You need to add a ReturnValue-direction parameter to the command:

using (SqlConnection conn = new SqlConnection(getConnectionString()))
using (SqlCommand cmd = conn.CreateCommand())
{
    cmd.CommandText = parameterStatement.getQuery();
    cmd.CommandType = CommandType.StoredProcedure;
    cmd.Parameters.AddWithValue("SeqName", "SeqNameValue");

    // @ReturnVal could be any name
    var returnParameter = cmd.Parameters.Add("@ReturnVal", SqlDbType.Int);
    returnParameter.Direction = ParameterDirection.ReturnValue;

    conn.Open();
    cmd.ExecuteNonQuery();
    var result = returnParameter.Value;
}

Setting the parameter's direction to ParameterDirection.ReturnValue instructs the SqlCommand to declare it as a variable and assign the stored procedure's return value to it (exec @ReturnValue = spMyProcedure...), exactly like you would write it in SQL.