Using LINQ to remove elements from a List<T>

Question

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 1

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)); 

Answer 2

It'd be better to use List<T>.RemoveAll to accomplish this.

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