手动从集合中删除项目与使用Enumerable.C＃除外

Question

To remove objects from a List of custom objects using Except method requires you to implement a IEqualityComparer on the object. But is it bad just to remove the objects in a normal foreach loop?

I understand the concept of the IEqualityComparer and using Except but I couldn't get it to work for some reason so I just removed the items manually. Is this considered bad programming?

EDIT: using the manual way id have to override Equals and GetHashcode polluting my view model - I guess that's bad?

Answer 1

In general, one should avoid making changes to a collection while enumerating.

I'm not entirely sure what your original problem is, or why you need to remove elements in such a way, but you're over-complicating the problem. If I understand it right, and you are in fact using a List<T> where T is a custom type. If this is the case, then simply use a LINQ query to get the values you want from the list.

var newList = oldList.Where(x => x.PropertyName != unwantedValue);

You could use Enumerable.Except , but it should be noted that Enumerable.Except returns a set , which is to say, no duplicate values are allowed.

Also, it should be noted that overriding .Equals and .GetHashCode does not pollute the viewmodel, as far as I know.

Sources:

http://msdn.microsoft.com/en-us/library/vstudio/bb336390(v=vs.100).aspx

Enumerable.Except Problem