LINQ group one type of item

Question

I have a List that has various derived classes. I may have something like this:

List<BaseClass> list = new List<BaseClass>() {
  new Class1(),
  new Class2(1),
  new Class3(),
  new Class2(2),
  new Class4()
};

I am trying to use LINQ to semi-sort the list so that the natural order is maintained EXCEPT for Class2. All Class2 instances should be grouped together at the place that the first Class2 occurs. Here is what the output should be like:

List<BaseClass> list = new List<BaseClass>() {
  new Class1(),
  new Class2(1),
  new Class2(2),
  new Class3(),
  new Class4()
};

I can't for the life of me figure out how to do this...

Answer 1

You can do it like this:

list = list
    .TakeWhile(o => !(o is Class2))
    .Concat(list.Where(o => o is Class2))
    .Concat(
        list.SkipWhile(o => !(o is Class2)).Where(o => !(o is Class2))
    )
    .ToList();

This will take all of the items until the first Class2 item, followed by all of the Class2 items, followed by all remaining non-Class2 items.