使用LINQ GroupBy获得不同的结果以实现复杂的实体关系？

Question

Here's a quick overview of my relationships:

one Account has many AccountRoles
one AccountRole has many UserAccountRoles
many UserAccountRoles can have one User

What I need to get is a set of all User s for one Account .

How can I do this in LINQ?

Edit:

Here's what I've tried so far:

var dto = _context.Set<Model.Account>()
    .Find(account.Id);

if (dto == null)
    return null;

var userAccountRoleDTOs = dto.AccountRoles
    .Select(ar => ar.UserAccountRoles);

var userDTOs = userAccountRoleDTOs
    .Select(uar => uar.Select(uar2 => uar2.User));

return userDTOs;

userDTOs is a collection of collections at the return . It doesn't make much sense to me.

Answer 1

Since ultimately all you want is a flattened collection for the one user, you should be able to use SelectMany() to flatten the one-to-many relationship and then call Distinct() at the end:

var users = dto.AccountRoles
    .SelectMany(ar => ar.UserAccountRoles.Select(uar => uar.User))
    .Distinct();

Or, in query form

var users = (from ar in dto.AccountRoles
             from uar in ar.UserAccountRoles
             select uar.User)
            .Distinct();

Answer 2

Or you can go the other way around:

from u in context.Users
where u.UserAccountRoles.Any(uar=>uar.AccountRole.Account.Id == someAccountId)