TK. TK. - 3 months ago 6
C# Question

Using LINQ to remove elements from a List<T>

Say that I have LINQ query such as:

var authors = from x in authorsList
where x.firstname == "Bob"
select x;


Given that
authorsList
is of type
List<Author>
, how can I delete the
Author
elements from
authorsList
that are returned by the query into
authors
?

Or, put another way, how can I delete all of the firstname's equalling Bob from
authorsList
?

Note: This is a simplified example for the purposes of the question.

Answer

Well, it would be easier to exclude them in the first place:

authorsList = authorsList.Where(x => x.FirstName != "Bob").ToList();

However, that would just change the value of authorsList instead of removing the authors from the previous collection. Alternatively, you can use RemoveAll:

authorsList.RemoveAll(x => x.FirstName == "Bob");

If you really need to do it based on another collection, I'd use a HashSet, RemoveAll and Contains:

var setToRemove = new HashSet<Author>(authors);
authorsList.RemoveAll(x => setToRemove.Contains(x));