Limit RemoveAll to a certain number of objects

Question

I am working with a List<T> which contains both parent and children objects. In this list children objects are aware of their related parent object and vice versa. Using this list I am trying to implement a business rule where up to 4 children objects will be removed from the list when their parent is of a certain type. Put differently if a parent of this type has 20 children 4 of them should be removed from the list.

The code I have outlined here will RemoveAll of the children objects that meet the condition. This is expected but what I'd like to do is limit the RemoveAll to removing only 4 children. Is there a means to do this with RemoveAll or is there another method I should be using?

myList.RemoveaAll(item =>
  item.Child && "Foo".Equals(item.Parent.SpecialType));

Answer 1

Why not use the Take function?

Answer 2

The Take extension method is used to grab the first n number of matches from an IEnumerable. You can then iterate through the matches and remove them from the list.

var matches = myList.Where(item => item.Child && "Foo".Equals(item.Parent.SpecialType)).Take(someNumber).ToList();
matches.ForEach(m => myList.Remove(m));

Answer 3

Does it matter which 4? If not, you can use .Take(4) to create a list of 4 children, then iterate through and Remove the 4...

Answer 4

try this:

int i = 0;
myList.Removeall(item =>
  item.Child && "Foo".Equals(item.Parent.SpecialType) && i++ < 4);

Note that I haven't tested it but it should work