无法翻译 LINQ 表达式

Question

I have a table called Orders and a list called Customers . Orders has a property CustomerId . Now I want to get all orders of customers that are in my Customers list.

This is what I tried:

IEnumerable<Customer> customers; // list of customers
List<Order> orders = dbContext.Orders.Where(x => customers.Any(y => y.Id == x.CustomerId)).Include(x => x.someOtherTable).ToList();

For some reason this always results in an exception saying that the LINQ expression could not be translated. My assumption is that this is due to the fact that the CustomerId in Order is nullable. I am not sure though.

Order :

public int Id { get; set; }
public int? CustomerId { get; set; } // has to be nullable
...

Customer :

public int Id { get; set; }
public string Name { get; set; } // has to be nullable
...

This is only a small snippet due to simplicity.

Answer 1

No, the reason is that customers is IEnumerable , not IQueryable , so LINQ can not transale to SQL code your collection.

Convert your IEnumerable<Customer> to id list:

int[] ids = customers.Select(o => o.id).ToArray();

And Where with Contains :

List<Order> orders = dbContext.Orders.Where(x => ids.Contains(x.Id))
                                     .Include(x => x.someOtherTable).ToList();

Answer 2

My issue was that I was using a read only property [x.Id] in the linq statement.

In my partial class:

public partial class Paddock
{
   public int Id => EntityId;
}

My linq query with error:

var paddocks = _context.Paddocks.Where(x => ids.Contains(x.Id)).ToList();

Changing it to the true property fixed it for me:

var paddocks = _context.Paddocks.Where(x => ids.Contains(x.EntityId)).ToList();