Create a list of objects by grouping on multiple properties

Question

I have a List<T> where T is a custom object Cow. Right now I use the following code to split that list up based on Color.

cowGroups = from x in cows
            group x by x.Color into y
            select y.ToList().ToList();

Then I take cowGroups and run a foreach on it to do a set of actions to each Cow. This list actually comes out as IEnumerable<List<Cow>>

What I'm trying to do is do a double grouping on my initial List<Cow> so that I can group base on their color and size. The result should still be IEnumerable<List<Cow>>, but each List<Cow> would be made based on the combined pair of color and size.

A co-worker recommended a ToLookup approach, but that returns a list of key/value pairs, and I can't seem to do anything with the value part of the pair.

I guess I'm looking for either a way to go straight to a collection of lists, or turn the result of the ToLookup approach into a collection of lists.

Andomar · Accepted Answer · 2013-05-13 20:07:22Z

5

You can group by a class that contains both attributes:

group x by new { x.Color, x.Size } into y

answered May 13, 2013 at 20:07

Andomar

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1 Comment

Logarr Over a year ago

Oh my... I feel so stupid now. One of the things I had tried was `cows.GroupBy(new {x.Color, x.Size}) but it resulted in a similar structure as ToLookup. EDIT: I should add that this is exactly what I needed. Thank you!

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