How to perform group by in LINQ and get a Iqueryable or a Custom Class Object?

问题

Here is my query -

var data = Goaldata.GroupBy(c => c.GoalId).ToList();

This returns a Igrouping object and I want an Iqueryable object which I can directly query to get the data while in this case I have to loop through using a foreach() and then get the data. Is there another way to group by in LINQ which returns directly as a list of Iqueryable or a List as similar to what happens for order by in LINQ.

回答1:

The easiest way is probably

var data = Goaldata.GroupBy(c => c.GoalId).SelectMany(c => c).ToList();

In the OO sense they aren't really grouped, but they are ordered with the groups together.

回答2:

Whilst the accepted answer is correct, it seems to be unnecessarily complicated. Assuming GoalId is an int you can just use OrderBy:

var data = Goaldata.OrderBy(c => c.GoalId).ToList();

回答3:

Or .GroupBy(c => c.GoalId).AsQueryable()...

来源：https://stackoverflow.com/questions/2837220/how-to-perform-group-by-in-linq-and-get-a-iqueryable-or-a-custom-class-object