Sql Server Must declare the scalar variable

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When one of asp.net project was in develop stage, we always got the exception 'Must declare the scalar variable "@variableName" '

I checked and searched from internet, about this issue, there have been many different reasons and solutons. But seems all of them are not fit our case.

I had to check by myself. I focused on this section of code:

       SqlConnection conn = new SqlConnection(DbConstants.ConnectionString);

         string sSql = "SELECT xSubID FROM  aTABLE " +
                " WHERE cID = @variableName";
        try
        {
            conn.Open();
           

SqlCommand myCommand = new SqlCommand(); myCommand.Parameters.AddWithValue("@variableName", contractorID); myCommand.Connection = conn; myCommand.CommandText = sSqlValidate;

            return int.Parse(myCommand.ExecuteScalar().ToString());
        }
        catch (Exception ex)
        {
            DB.AddToExceptionLog(ex);
        }
        finally
        {
            conn.Close();
        }

I tried to change to the following code:

       SqlConnection conn = new SqlConnection(DbConstants.ConnectionString);

         string sSql = "SELECT xSubID FROM  aTABLE " +
                " WHERE cID = @variableName";
        try
        {
            conn.Open();
           

//Why I changed to this just because I suppose the SQLCommandType should be given, in this case , The SQLCommandType is text, but also I suppose the following code has implidly set the SQLCommandType SqlCommand myCommand = new SqlCommand(sSql, conn); myCommand.Parameters.AddWithValue("@variableName", cID);

            return int.Parse(myCommand.ExecuteScalar().ToString());
        }
        catch (Exception ex)
        {
            DB.AddToExceptionLog(ex);
        }
        finally
        {
            conn.Close();
        }