c# - LINQ query to find if items in a list are contained in another list

Question

I have the following code:

List<string> test1 = new List<string> { "@bob.com", "@tom.com" };
List<string> test2 = new List<string> { "[email protected]", "[email protected]" };

I need to remove anyone in test2 that has @bob.com or @tom.com.

What I have tried is this:

bool bContained1 = test1.Contains(test2);
bool bContained2 = test2.Contains(test1);

bContained1 = false but bContained2 = true. I would prefer not to loop through each list but instead use a Linq query to retrieve the data. bContained1 is the same condition for the Linq query that I have created below:

List<string> test3 = test1.Where(w => !test2.Contains(w)).ToList();

The query above works on an exact match but not partial matches.

I have looked at other queries but I can find a close comparison to this with Linq. Any ideas or anywhere you can point me to would be a great help.

Answer 1

var test2NotInTest1 = test2.Where(t2 => test1.Count(t1 => t2.Contains(t1))==0);

Faster version as per Tim's suggestion:

var test2NotInTest1 = test2.Where(t2 => !test1.Any(t1 => t2.Contains(t1)));