Question

All, I have come across the following property and object declaration. The first returns an interface, and the second I am not too sure about

public IConfig this[int index]
{
    get { return (IConfig)configList[index]; }
}

object IList.this[int index]
{
    get { return configList[index]; }
    set {  }
}

I have never seen this type of declaration, namely the public IConfig this[int index] with square brackets and the odd use of this and object IList.this[int index]. Can some one explain the two notations?

I have attempted to look in the books I have, and use Google but I am unsure what I am searching for. Thanks for your time.

Edit. These are in a class that inherits as follows

public class ConfigCollection : ICollection, IEnumerable, IList
{
    ....
}

Answer 1

It is called an indexer and allows you to do instance[1]; when getting an element from your object. You can have a look at this answer on implementing IList as a reference