#365 – Overloading an Indexer

You can define several versions of an indexer in a class, each indexed using a different type, overloading the indexer.

In the example below, we can index using the Days enumerated type or a 0-based integer representing the day.

    public class Logger
    {
        private Dictionary<Days, LogMessage> dailyMessages = new Dictionary<Days, LogMessage>();

        public LogMessage this[Days day]
        {
            get { return dailyMessages[day]; }
            set { dailyMessages[day] = value; }
        }

        public LogMessage this[int i]
        {
            get { return dailyMessages[(Days)i]; }
            set { dailyMessages[(Days)i] = value; }
        }
    }

Using this class, we could then index using either the Days or the integer type.

            Logger log = new Logger();

            log[Days.Mon] = new LogMessage("Monday was a good day");
            log[2] = new LogMessage("Tuesday not bad either");

In this example, we indexed into the same internal data object.  But we could have also indexed into different objects, depending on the indexer’s type.