无法翻译 EF Core Linq 表达式

Question

I have an issue with an EF Core query when I'm filtering against a nullable Guid property, for example

public class Order 
{
  public Guid? MachineId {get;set;}
}

I'm trying to filter orders based on a list of MachineId s

var machineIds // a list of Guids

var orders = _context.Orders.Where(x => machineIds.Contains(x.MachineId.GetValueOrDefault()));

The error I'm getting is

System.InvalidOperationException : The LINQ expression 'DbSet<Orders>
        .Where(x => __machineIds_0
            .Contains(m.MachineId.GetValueOrDefault()))' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to either AsEnumerable(), AsAsyncEnumerable(), ToList(), or ToListAsync(). See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

I'm not sure how to express this query another way - can anyone help?

Answer 1

Converting the list of Guids to a list of nullable Guids resolves the issue (thanks mjwills ).

var machineIds = machines
  .Select(x =>  new Guid?(x.Id)); 

The EF Core query becomes

var orders = _context.Orders.Where(x => machineIds.Contains(x.MachineId));

Answer 2

I'd suggest removing the use of .GetValueOrDefault() and make machineIds a list of nullable guids (rather than guids).

This might look like:

var machineIds = new List<Guid?>();

var orders = _context.Orders.Where(x => machineIds.Contains(x.MachineId));

Answer 3

_context.Orders.Where(order => MachineIds.Where(Id => Id == order.MachineId).Any())

This is untested. Modifications might be necessary.