Possibility of static indexers in C#

class Test
{
    static Dictionary<int, string> map = new Dictionary<int, string>();

    private Test() { }

    private static Test instance = new Test();

    internal static Test Instance
    {
        get { return Test.instance; }
    }

    public string this[int i]
    {
        get
        {
            return map[i];
        }

        set
        {
            map[i] = value;
        }
    }
}

Test.Instance[3] = "hello";
string s = Test.Instance[3];