Split a list into sublist by a separator not by index in C#

I'm not aware of an existing operator to do this in LINQ to Objects itself, more the MoreLINQ project has the Split method, so you can use:

var sections = originalList.Split("-----");

That returns an IEnumerable<IEnumerable<string>> - if you need a list of lists, you could use:

var sections = originalList.Split("-----")
                           .Select(section => section.ToList())
                           .ToList();

MoreLINQ has a NuGet package that you might wish to use for installation.