Question

This:

List<string> set = new List<string>() { "a","b" };

works fine, but:

Stack<string> set = new Stack<string>() { "a","b" };
Queue<string> set = new Queue<string>() { "a","b" };

fails with:

...does not contain a definition for 'Add'

which does make me wonder why the compiler was dumb enough to ask for Add.

So, how should one initialise at a Queue/Stack constructor?

Answer 1

Collection initializers are a compiler feature that call the Add method with each item you pass.
If there is no Add method, you can’t use it.

Instead, you can call the Stack or Queue constructor that takes an IEnumerable<T>:

var stack = new Stack<int>(new [] { 1, 2, 3 });