Question

I’m trying to use Command.Prepare with a CommandType.Text query that has a single input parameter. The SELECT has several columns that I am extracting with a DataReader. Do I need to specify each of the select columns as output parameters before calling Command.Prepare()? Even if I don’t need to specify them, will performance improve if I do?

Example code:

using(var connection = new SqlConnection("connection string")
{
    connection.Open();
    using(var cmd = new SqlCommand(null, Connection))
    {
        cmd.CommandText = "SELECT COLUMN1, COLUMN2, COLUMN3 " + 
                          "FROM TABLE1 WHERE COLUMN4 = @thing";
        cmd.Parameters.Add(new SqlParameter
                               {
                                   ParameterName = "@thing",
                                   DbType = SqlDbType.Int,
                                   Value = 1
                                });
        //should I add output parms for COLUMN1, COLUMN2, COLUMN3?
        cmd.Prepare();
        using(var reader = cmd.ExecuteReader())
        {
            //get stuff out of reader
        }
    }
}

Answer 1

No, you don’t need output parameters. You just get the results out of the reader in the normal way.

In fact, having the columns as output parameters wouldn’t make sense, as you’ll have a value per column per row rather than just one value for the whole call.