LINQ to实体C＃分组依据/不同查询

Question

I have a Linq to Entity query that pulls out photos of my database. My ultimate goal is just to get the size and sum them up but I need to do a distinct call on the ID first because I am grouping the call and obviously there could be multiple records with the same photo size so I cant call distinct on that. So how would I call a distinct on the photoID but pull the photo size? thanks for any help.

from x in _context.Clients
join media in _context.Mediae 
on x.ID equals media.ClientID into Medias
from submedia in Medias.DefaultIfEmpty()
group new { x.ClientName, submedia } by new { x.ClientName } into g

//I would like to get the Sum of the MediaSize out of this But I call distinct on ID                       
let mediaCount = g.Where(x=>x.submedia  != null).Select(x=>x.submedia .ID).Distinct()
//Example of what I wish would work below
//g.Where(x => x.subEventMedia != null).Select(x => x.subEventMedia.ID).Distinct().Sum(x => x.subEventMedia.MediaSize)

Answer 1

You can use GroupBy and the select the first item in that group to get the effect of a DistinctBy .

let mediaCount = g.Where(x=>x.submedia != null)
    .GroupBy(x=>x.submedia.ID)
    .Sum(mediaGroup => mediaGroup.FirstOrDefault().submedia.MediaSize)