System.Data.SqlTypes.SqlString.ToString C# (CSharp) Method

        public override string ToString()
        {
            return IsNull ? SQLResource.s_nullString : _value;
        }

    public static IEnumerable FindPHkeysAndSlots(SqlInt16 partsnap, SqlInt16 fofsnap, SqlString temp_partid_table_name, SqlInt32 numparts)
    {
        //string temp_partid_table = "#temp_partid_list";
        List<PhkeySlot> keysAndSlots = new List<PhkeySlot>();
        using (SqlConnection connection = new SqlConnection("context connection=true"))
        {
            connection.Open();
            string getFoFGroupIDsCommandString = "select partid from " + temp_partid_table_name.ToString();
            SqlCommand getFoFGroupIDsListCommand = new SqlCommand(getFoFGroupIDsCommandString, connection);
            SqlDataReader getFOFGroupIDsReader = getFoFGroupIDsListCommand.ExecuteReader();
            Int64[] partids = new Int64[(int) numparts];
            int numlines = 0;
            while (getFOFGroupIDsReader.Read())
            {
                partids[numlines] = Int64.Parse(getFOFGroupIDsReader["partid"].ToString());
                ++numlines;
            }
            getFOFGroupIDsReader.Close();
            // Find the index blocks we need to look in
            HashSet<Int64> blocks = new HashSet<Int64>();
            foreach (Int64 id in partids)
            {
                blocks.Add((id - 1) / 1024 / 1024);
            }

            //means we want all snaps
            string rawCommand = "";
            if (partsnap < 0)
            {
                rawCommand = "select a.snap, a.phkey, a.slot from particleDB.dbo.index{0} a, " + temp_partid_table_name.ToString() + " b "
                    + " where a.partid = b.partid";
            }
            else
            {
                rawCommand = "select a.snap, a.phkey, a.slot from particleDB.dbo.index{0} a, " + temp_partid_table_name.ToString() + " b "
                    + " where a.partid = b.partid and a.snap = @partsnap";
            }

            foreach (Int64 blockID in blocks)
            {
                string joinFoFGroupIndexCommandString = string.Format(rawCommand, blockID);
                SqlCommand joinFofGroupIndexCommand = new SqlCommand(joinFoFGroupIndexCommandString, connection);
                SqlParameter partsnapParam = new SqlParameter("@partsnap", System.Data.SqlDbType.SmallInt);
                partsnapParam.Value = partsnap;
                joinFofGroupIndexCommand.Parameters.Add(partsnapParam);
                SqlDataReader joinReader = joinFofGroupIndexCommand.ExecuteReader();
                while (joinReader.Read())
                {
                    int snap = Int32.Parse(joinReader["snap"].ToString());
                    int phkey = Int32.Parse(joinReader["phkey"].ToString());
                    short slot = Int16.Parse(joinReader["slot"].ToString());
                    PhkeySlot current = new PhkeySlot(snap, phkey, slot);
                    keysAndSlots.Add(current);
                }
                joinReader.Close();
            }
        }
        return keysAndSlots;
    }