To use initialization syntax like this:

var contacts = new ContactList
{
    { "Dan", "[email protected]" },
    { "Eric", "[email protected]" }
};

...my understanding is that my ContactList type would need to define an Add method that takes two string parameters:

public void Add(string name, string email);

What's a bit confusing to me about this is that the { } initializer syntax seems most useful when creating read-only or fixed-size collections. After all it is meant to mimic the initialization syntax for an array, right? (OK, so arrays are not read-only; but they are fixed size.) And naturally it can only be used when the collection's contents are known (at least the number of elements) at compile-time.

So it would almost seem that the main requirement for using this collection initializer syntax (having an Add method and therefore a mutable collection) is at odds with the typical case in which it would be most useful.

I'm sure I haven't put as much thought into this matter as the C# design team; it just seems that there could have been different rules for this syntax that would have meshed better with its typical usage scenarios.

Am I way off base here? Is the desire to use the { } syntax to initialize fixed-size collections not as common as I think? What other factors might have influenced the formulation of the requirements for this syntax that I'm simply not thinking of?