c# - Linq query select distinct Order

Question

I would like to get orders and joining another table and the problem is there's duplicate order returns.

Order table
Id  OrderNumber UserId
1   Ord123      U1
2   Ord124      U2
3   Ord125      U3
4   Ord126      U2

Authorize Customer Table
Id  UserId      CustomerId
1   U1      U2
2   U3      U2

Current Result for User: U1 (Power User) in viewing orders

Orders
Id  OrderNumber UserId
1   Ord123      U1
2   Ord124      U2
2   Ord124      U2
4   Ord126      U2
4   Ord126      U2

I want like this result

Id  OrderNumber UserId
1   Ord123      U1
2   Ord124      U2
4   Ord126      U2

So orders of User: U2(Customer) can be viewed by User: U1(Power User) and U3 (Support User). Below is my current implementation in querying orders.

 orders = 
    from items in ctx.Orders
    join auc in ctx.UserAuthorisedCustomers
    on items.UserId equals auc.CustomerId
    into jts
    from jtResult in jts.DefaultIfEmpty()
    where jts.Any(x => x.UserId == cri.UserId && x.CustomerId == items.UserId) 
      || items.UserId == cri.UserId
    select items;

And cri.UserId is User: U1

question from:https://stackoverflow.com/questions/66056770/linq-query-select-distinct-order

Answer 1

You are almost there, you just need to include the Distinct() function from your linq query, but to make sure you can adjust your SQL query data to C# code, you need to convert your linq query result to c# List() so the code would look like

 orders = 
from items in ctx.Orders
join auc in ctx.UserAuthorisedCustomers
on items.UserId equals auc.CustomerId
into jts
from jtResult in jts.DefaultIfEmpty()
where jts.Any(x => x.UserId == cri.UserId && x.CustomerId == items.UserId) 
  || items.UserId == cri.UserId
select items;

var distinct_orders = orders.ToList().Distinct();