Question

List<string> a = new List<string>() { "a", "b", "c" };
List<string> b = new List<string>() { "a", "b", "c", "d", "e", "f" };

b.RemoveAll(a.Contains);

If you loop through b it will now only contain d e and f. Can anyone expand out whats actually happening, because currently it doesnt make any sense at all.

Edit: I was more talking about the use of predicates. How does know how to pass what into where?

Answer 1

b.RemoveAll(<function that takes a string and returns true if we want to remove it>)

no lambda expression required.

perhaps you’d like for the line to read

b.RemoveAll(x => a.Contains(x))

however, the function x=> a.Contains(x) is simply a function that takes a string and returns a bool indicating whether a contains x. a.Contains is already a function that does that.