Have trouble reading a null returned from stored procedure

Question

I have a stored procedure that returns a single record, either null or data if present.

In my code I need to check what that procedure returns. What is the right way to do it?

Now when, running the code I have an exception saying: "Invalid attempt to read when no data is present." I'm using Visual Studio 2005.

Here is my method:

public static String GetRegionBasedOnIso(String isoNum)
    {
        SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["MyConn"].ConnectionString);
        String region = null;
        try
        {
            using (SqlCommand cmd = new SqlCommand("MyProc", conn))
            {
                conn.Open();
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@isoNum", isoNum);
                using (SqlDataReader dr = cmd.ExecuteReader())
                {
                    if (dr.IsDBNull(0))
                    {
                        return null;
                    }
                    else
                    {
                        region = (String)dr["region"];
                    }
                }
            }
        }
        catch (Exception e)
        {
            throw new System.Exception(e.Message.ToString());
        }
        finally
        {
            conn.Close();
        }
        return region;
    }

What can I do to fix it? Thank you

Answer 1

if (dr.Read())
{
    if (dr.IsDBNull(0))
    {
        return null;
    }
    else
    {
        region = (String)dr["region"];
    }
}
else
{
    // do something else as the result set is empty
}