How to convert SQL query to Linq in Entity Framework 6?

Question

How can I convert this SQL query to a linq expression?

Select distinct Clients.Id 
From Clients
Join Orders On Clients.Id = Orders.ClientsId and Orders.Date < DATEADD(DD, -Clients.Term, CAST(GETDATE() AS DATE))

Yes, I know about the Database.SqlQuery<>() function. Probably it's the best solution in terms of performance. But code uniformity is preferred, so I need to use linq.

Here is my solution:

var outdatedClients = context.Clients.GroupJoin(context.Orders,
client => client.Id,
order => order.ClientId,
(client, order) => new 
{
    Id = client.Id,
    Term = client.Term,
    Orders = order.Any(order => DbFunctions.DiffDays(order.Date, _datenow) > client.Term)
})
.ToList()
.Where(client => client.Orders == true);

But maybe it`s possible to do it more elegantly?

Answer 1

This is all freehand so I apologize if there are some syntax issues...

Assuming you are using EF/EFCore and your classes are structured similar to the following:

public class Client
{
    public Guid Id { get; set; }
    public int Term { get; set; }
    public virtual ICollection<Order> Orders { get; set; }
}

public class Order
{
    public Guid Id { get; set; }
    public Guid ClientId { get; set; }
    public DateTime Date {get; set; }
}

Then something like the following should match your SQL query?:

var clients = await context.Clients.Include(c => C.Orders)
.Where(c => c.Orders.Any(o => o.Date < DateTime.Now.AddDays(-c.Term)))
.ToArrayAsync();

You could also distinct the result, but assuming that 'Id' is your primary key for Client then it shouldn't be necessary as they will be unique.