how to flatten out webapi EF using DTO and linq - entity-framework

Question

I am trying to flatten out my webapi EF using a DTO and linq but not quite sure how to do it. My end goal is to say, I want to return ALL four accounts where USERNAME = x.
In this example there is 1 username with access to 1 client, and that 1 client has 4 accounts.
How can I make the result come back with 4 entries, 1 for each account?
Here is what I have so far...
var x2 = from b in db.AspNetUsers
where b.UserName == username
select new AspNetUserDetailDTO()
{
UserName = b.UserName,
Email = b.Email,
Mapping_UserClient = b.Mapping_UserClient
//ClientName = b.Mapping_UserClient.SelectMany<Mapping_UserClient>(x => x.ClientID)
//Mapping_UserClient = b.Mapping_UserClient
};
below is my sql diagram.
so I tried writing a plain sql query to return a basic result of what I am looking for... now I do not know how to do this in LINQ
SELECT
dbo.Clients.ClientName
,dbo.Mapping_UserClient.ClientID
,*
FROM [xxx].[dbo].[AspNetUsers]
inner join dbo.Mapping_UserClient on dbo.Mapping_UserClient.AspNetUsersID = dbo.AspNetUsers.Id
inner join dbo.Clients on dbo.Clients.ClientID = dbo.Mapping_UserClient.ClientID
inner join dbo.Mapping_ClientAccount on dbo.Mapping_ClientAccount.ClientID = dbo.Clients.ClientID
inner join dbo.Accounts on dbo.Accounts.AccountID = dbo.Mapping_ClientAccount.AccountID
where Email = 'dddd'

Answer 1

Translating your query above, you would get something like this in Linq:
var query = (from acc in db.Accounts
join mca in db.Mapping_ClientAccount
on acc.AccountId equals mca.ClientID
join cli in db.Clients
on mca.ClientID equals cli.ClientID
join muc in db.Mapping_UserClient
on cli.ClientID equals muc.ClientID
join anu in db.AspNetUsers
on muc.AspNetUsersID equals anu.Id
where anu.UserName == username
select new AspNetUserDetailsDTO()
{
ClientName = cli.ClientName,
ClientID = cli.ClientID
}).ToList();