空检查会导致客户端评估吗？

Question

我想问一下为什么要在客户端评估这样的查询：

_context
    .Items
    .Include(x => x.Status)

    .Include(x => x.Orders)
    .ThenInclude(x => x.User)

    .Include(x => x.Orders)
    .ThenInclude(x => x.OrderStatus)

    .Where(x => x.Orders.Any())
    .Where(x => x.Order != null)
    .Where(x => x.Order.User.SomeProperty.ToLower() == user.SomeProperty.ToLower());

user.SomeProperty.ToLower() 中使用的用户只是身份用户，它不为空。

public class Item
{
    public Guid Id = { get; protected set; }

    public List<Order> Orders { get; set; } = new List<Order>();

    public Order Order => Orders.FirstOrDefault(x => x.OrderStatus.Name = "Active");

    public Status Status { get; set; }
}

public class Order
{
    public Guid Id = { get; protected set; }

    public User User = { get; set; }

    public Status OrderStatus = { get; set; }
}

public class Status
{
    public Guid Id = { get; protected set; }

    public string Name = { get; set; }
}

EF Core 警告说空检查是原因之一，但我不明白为什么不能翻译空检查

警告：Microsoft.EntityFrameworkCore.Query[20500] LINQ 表达式 'where (Property([x].Order, "Id") != null)' 无法翻译，将在本地计算。

警告：Microsoft.EntityFrameworkCore.Query[20500] 无法翻译 LINQ 表达式“where ([x].Order.User.SomeProperty==__user_SomeProperty_0)”，将在本地进行计算。

Answer 1

EF 无法翻译方法或属性中的查询。移动这个

public Order Order => Orders.FirstOrDefault(x => x.OrderStatus.Name = "Active");

到实际查询

编辑。您可以使用扩展方法来重用查询

edit2：创建扩展方法

public static class FooQueryExtensions
{
   public static IQueryable<FooResult> MyFooQuery(this IQueryable<Foo> source)
   {
      return source.SelectMany(...).Where(...); //basicly do what yuo want
   }
}

习惯了

_context.Set<Foo>().MyFooQuery().Where(result => more query);