My suggestion would be to look into the Enumerable.GroupBy
] extension method. You can then use Enumerable.Select
] and Enumerable.SelectMany
] to manipulate the results into the form you want.
As an aside: spending a little time to make your question clearer and easier to read can make people more willing to answer your questions. For layouts like the one you've used to represent your tables, <pre> tags are your friend, as they are shown using a fixed-width font.