LINQ query for joining multiple tables and get comma separated values in single row - entity-framework

Question

I have below tables with the values.
Account:
Id
Name
Email
101
Nasir Uddin
nasir#email.com
Role:
Id
Title
101
Admin
102
Operator
AccountRole:
AccountId
RoleId
101
101
101
102
Now I want to write a linq to have the result like below:
UserAccount
AccountId
Name
Email
Roles
101
Nasir Uddin
nasir#email.com
Admin, Operator
To get the above result I have written the below query in LINQ. But it does not get the expected result.
var userAccount1 = (from account in _db.Accounts
join accountRole in _db.AccountRoles on account.Id equals accountRole.AccountId
join role in _db.Roles on accountRole.RoleId equals role.Id
select new UserAccountInfo
{
AccountId = account.Id,
Name = account.UserFullName,
Email = account.Email,
Roles = string.Join(",", role.Title)
});

Answer 1

At last I found my answer. The results can be achieved in different ways. Examples are given below:
var answer1 = (from account in userAccounts
join accountRole in accountRoles on account.Id equals accountRole.AccountId
join role in roles on accountRole.RoleId equals role.Id
select new UserAccount
{
AccountId = account.Id,
Name = account.Name,
Email = account.Email,
Roles = role.Title
}).ToList().GroupBy(x => new { x.AccountId, x.Name, x.Email }).Select(y => new UserAccount
{
AccountId = y.Key.AccountId,
Name = y.Key.Name,
Email = y.Key.Email,
Roles = string.Join(", ", y.Select(a => a.Roles))
}).ToList();
----------------------------------------------------------------------------
var answer2 = (from account in userAccounts
join accountRole in accountRoles on account.Id equals accountRole.AccountId
join role in roles on accountRole.RoleId equals role.Id
group new { account, role } by new { account.Id, account.Name, account.Email } into ag
select new UserAccount
{
AccountId = ag.Key.Id,
Name = ag.Key.Name,
Email = ag.Key.Email,
Roles = string.Join(", ", ag.Select(x=> x.role.Title))
}).ToList();
----------------------------------------------------------------------------
var answer3 = (from account in userAccounts
let roles1 = from accountRole in accountRoles
join role in roles on accountRole.RoleId equals role.Id
where accountRole.AccountId == account.Id
select role
select new UserAccount
{
AccountId = account.Id,
Name = account.Name,
Email = account.Email,
Roles = string.Join(", ", roles1.Select(x => x.Title))
}).ToList();

Answer 2

The below gives you the expected result using Lambda Expression (not Query Expression) based on the information provided in your post (and some assumptions since I could not find e.g. UserFullName in any of your tables)
Note: I'm also convinced there is a more efficient way to do this, but it is a starting point if nothing else.
(Here is working .NET Fiddle of the below: https://dotnetfiddle.net/aGra15):
// Join the AccountRoles and Roles together and group all Titles for
// a given AccountId together
var groupedAccountRoles = AccountRoles.GroupJoin(Roles, i => i.RoleId, o => o.Id, (o, i) => new {o, i})
.Select(x => new {AccountId = x.o.AccountId, Titles = string.Join(",", x.i.Select(y => y.Title))});
// Perform another GroupJoin to group by AccountId and Join to groupedAccountRoles table. Then `string.Join()`
var userAccount1 = Accounts.GroupJoin(AccountRoles, acc => acc.Id, accrol => accrol.AccountId,
(o, i) => new {o, UserAccountRoles = i})
.GroupJoin(groupedAccountRoles, ii => ii.o.Id, oo => oo.AccountId,
(ii, oo) => new UserAccountInfo
{
AccountId = ii.o.Id,
Email = ii.o.Email,
Name = ii.o.Name,
Roles = string.Join(",", oo.Select(x => x.Titles))
});
This will give the following output: