IDataReader.GetOrdinal or IDataReader[ColumnName]

Question

I have two cases to extract information from the IDataReader object

Case - 1 - Length, calculates ordinal and then parse string

public static string GetString(IDataReader rdr, string columnName)
{
    int ordinal = rdr.GetOrdinal(columnName);
    if (rdr.IsDBNull(ordinal))
    {
        return string.Empty;
    }
    return (string)rdr[ordinal];
}

---

Case - 2, short way, getting data without calculating ordinal

public static string GetString(IDataReader rdr, string columnName)
{
    return (string)rdr[columnName];
}

Which technique should be preferred and why and if any specific context ?

Answer 1

SqlDataReader's this[string name] looks like:

public override object this[string name]
{
    get
    {
        return this.GetValue(this.GetOrdinal(name));
    }
}

so it calculates ordinal internaly, and there is no difference what way to use.

UPDATE

Yo can rewrite your code as:

public static string GetString(IDataReader rdr, string columnName)
{
    return (rdr[columnName] as String)??String.Empty;
}