C# Compare two ulong lists and subtract extraneous ulong's from the unprotected one

I have two lists of Ulongs:

The first list is a list of ulongs , the second is a (larger) list of ulongs that should be protected.

I want to somehow compare the two lists, and remove any ulongs that the f开发者_如何学编程irst list has that the protected list does not have (sort of garbage collection I guess).

What would be the recommended way to handle this?

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What you are after is intersection.

var source = Enumerable.Range(1, 10);
var protectedSet = Enumerable.Range(9, 4);
var result = protectedSet.Intersect(source);

Which would result in:

source:

1
2
3
4
5
6
7
8
9
10

protectedSet:

9
10
11
12

result intersection:

9
10