比较两个列表，使它们在元素中相等

Question

I have two lists named List1 & List2.

Now say List1 & List2 has 5 elements {a,b,c,d,e}. Now if I remove {b,c} from List1 and add {f,g,h} to List1, how can i make List2 Equal(by doing add & remove operation on it.).

Answer 1

"(by doing add & remove operation on it.)"

Why this constraint?
The easiest, most reliable and probably the fastest way:

List2 = List1.ToList();

But if you really want it:

List2.RemoveRange(List2.Except(List1));  // You may have to write RemoveRange()
List2.AddRange(List1.Except(List2));

Answer 2

Let the List2 be just a reference of List1, for example:

List<string> list1 = new List<string>();
List<string> list2 = list1;

Modifying the list1 will affect the list2 as well

Answer 3

The @Henk Holterman suggests the right way(on the first part of the answer), but if you want exactly what you mentioned in OP then you can use this

list2.RemoveAll(l => !list1.Contains(l));
list2.AddRange(list1.Except(list2));