LINQ: A better way to grouping a list of objects by multiple properties in to a list of lists?

c#, linq, list

Solution

Just do:

List<List<Campaign>> groups = cmps.GroupBy(c => new { c.Id, c.Name })
    .Select(group => group.ToList())
    .ToList();

GroupBy on IEnumerable returns `IEnumerable<IGrouping<TKey, T>>`. `IGrouping<TKey, T>` implements `IEnumerable<T>`, so you can just use the group directly as a sequence.

Problem

I have a list of objects as such: ``` var cmps = new List<Campaign>() { new Campaign(){ PersonId = 1, Id = 1, Name = "Name"}, new Campaign(){ PersonId = 2, Id = 1, Name = "Name"}, new Campaign(){ PersonId = 3, Id = 1, Name = "Name1"}, new Campaign(){ PersonId = 4, Id = 2, Name = "Name1"}, new Campaign(){ PersonId = 5, Id = 2, Name = "Name1"}, new Campaign(){ PersonId = 6, Id = 3, Name = "Name"}, }; ``` I want to group them into a list of lists by the multiple properties, in this example by `Id` and `Name`. This would split the original list into the following (where the number represents `PersonId`): {[1, 2], [3], [4, 5], [6]} I have solved this by writing the following code: ``` List<List<Campaign>> groups = cmps.GroupBy(c => new { c.Id, c.Name }) .Select(c => c.Key) .ToList() .Select(v => cmps.Where(c => c.Id == v.Id && c.Name == v.Name).ToList()) .ToList(); ``` This solution seems to be working fine, but out of curiosity, is there a nicer/better way to do this?

Original source