How can I know if ListA has everything ListB has?

Question

If I have the following...

List<string> listA = new List<string>();
listA.Add("a");
listA.Add("b");
listA.Add("c");
listA.Add("d");

List<string> listB = new List<string>();
listB.Add("b");
listB.Add("d");

How can I know if listA has everything listB has?

Asked several times. Please do some research. http://stackoverflow.com/questions/1520642/does-net-have-a-way-to-check-if-list-a-contains-all-items-in-list-b — MickJ, Apr 02 '13 at 15:14

score 10 · Accepted Answer · answered Apr 02 '13 at 15:14

10

Using Enumerable.Except

bool allBinA = !listB.Except(listA).Any();

Demo

answered Apr 02 '13 at 15:14

Tim Schmelter

450,073
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score 2 · Answer 2 · answered Apr 02 '13 at 15:14

you could do it the raw (slow) way to make sure

bool contains_all = true;

foreach(String s in listA) {
  if(!listB.Contains(s)) {
    contains_all = false;
    break;
  }
}

although this does perform an exhaustive search on every element within the array

score 0 · Answer 3 · answered Apr 02 '13 at 15:13

0

Try this:

bool result = listB.Intersect(listA).Count() == listB.Count;

And also this:

bool result2 = listB.Select(input => !listA.Contains(input)).Count() > 0;

answered Apr 02 '13 at 15:13

Hossein Narimani Rad

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2

What if list A has more than list B? – George Duckett Apr 02 '13 at 15:14

score 0 · Answer 4 · answered Apr 02 '13 at 15:15

0

bool result = false;

if (listB.Count>listA.Count) result =  listB.Intersect(listA).Count() == listB.Count;

else result =  listA.Intersect(listB).Count() == listA.Count;

answered Apr 02 '13 at 15:15

enb081

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How can I know if ListA has everything ListB has?

4 Answers4