Implementing indexing "operator" in on a class in C#

Question

How would one go about implementing the indexing "operator" on a class in C# ?

class Foo {

}

Foo f = new Foo();
f["key"] = "some val";
f["other key"] = "some other val";

in C# ? Searched MSDN but came up empty.

Answer 1

    private List<string> MyList = new List<string>();
    public string this[int i]
    {
        get
        {
            return MyList[i];
        }
        set
        {
            MyList[i] = value;
        }

    }

You can define several accessors for different types (ie string instead of int for example) if it's needed.

Answer 2

Here is an example using a dictionary as storage:

public class Foo {

 private Dictionary<string, string> _items;

 public Foo() {
  _items = new Dictionary<string, string>();
 }

 public string this[string key] {
  get {
   return _items[key];
  }
  set {
   _items[key]=value;
  }
 }

}

Answer 3

There called Indexers or sometimes Indexer Properties.

Here's the MSDN page about them.