.NET Dictionary: get or create new

Question

I often find myself creating a Dictionary with a non-trivial value class (e.g. List), and then always writing the same code pattern when filling in data.

For example

Answer 1

If you use .Net Core you can use Dictionary<>.TryAdd().

var dict = new Dictionary();
dict.TryAdd("foo", "bar"); // returns bool whether it added or not feel free to ignore.
var myValue = dict["foo"];