How to make inline array initialization work like e.g. Dictionary initialization?

Question

Why is it possible to initialize a Dictionary like this:

var dict = new Dictionary() { 
    { \"key1\", 1 },
    { \"         


        

Answer 1

Override IDictionary for the C# 6.0 syntax

In case someone comes here, as I did, looking to save some keystrokes for the new C# 6.0 dictionary initializer syntax, it can be done, but requires deriving from IDictionary instead. You only need to implement the this[] set method to get this to work, which leaves a ton of non-implemented methods.

The class implementation looks like this:

// Seriously!  Don't do this in production code! Ever!!!
public class CrazyAdd2 : IDictionary
{
    public int this[string key]
    {
        get { throw new NotImplementedException(); }
        set {Console.WriteLine($"([{key}]={value})"); }
    }

#region NotImplemented
// lots of empty methods go here
#endregion
}

then to use it:

var crazyAdd2 = new CrazyAdd2
{
    ["one"] = 1,
    ["two"] = 2,
};

and the output:

([one]=1)
([two]=2)

And here's a fiddle demonstrating the whole thing:

https://dotnetfiddle.net/Lovy7m