Question

我想问为什么在客户端对这样的查询进行评估：

_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());

在user.SomeProperty.ToLower()中使用的用户仅仅是身份用户，并且不为空。

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核心警告说空检查是原因之一，但我不明白为什么无法翻译空检查

警告：Microsoft.EntityFrameworkCore.Query [20500]   LINQ表达式'where（Property（[x] .Order，“ Id”）！= null）'）无法翻译，将在本地进行评估。

警告：Microsoft.EntityFrameworkCore.Query [20500]   LINQ表达式'where（[x] .Order.User.SomeProperty == ____ user_SomeProperty_0）'无法翻译，将在本地进行评估。

Answer 1

EF无法在方法或属性中转换查询。移动

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
   }
}

使用方式

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

空检查可以引起客户端评估吗？

1 个答案: