LINQ way to check if a list contains an object from another list-CodePudding

I have a List of objects and I want to check if a different List contains a certain object. I have written some code that works for it I just couldn't quite figure out a way to do it with LINQ (if possible)

                        foreach (var file in files)
                        {
                            if (!pushedList.Contains(file))
                            {
                                myStack.Push(file);
                                pushedList.Add(file);
                            }
                        }

Something like if (!pushedList.Contains(files.Select(f => f))) except I just want to select the 1 file that is inside of files. The two List's in question are files and pushedList

CodePudding user response：

Since LINQ is for querying and not modifying, you just use it to figure out the files you need to process, then do the processing on those files:

var missingFiles = files.Where(f => !pushedList.Contains(f)).ToList();
myStack.PushRange(missingFiles);
pushedList.AddRange(missingFiles);

Depending on the sizes, it may be worthwhile to make a HashSet from pushedList before doing the query, or ideally, make pushedList a HashSet instead of a List.