System.NotSupportedException：无法在LINQ to Entities查询中构造实体或复杂类型“Resturant.Models.RestaurantViewModel” [英] System.NotSupportedException: The entity or complex type 'Resturant.Models.RestaurantViewModel' cannot be constructed in a LINQ to Entities query

问题描述

我写了一个如下查询：

I have written a query which is as follows:

var model = (from r in _db.Restaurants
     join rev in _db.Reviews
     on r.Id equals rev.RestaurantId
     into rest_rev
     from rr in rest_rev.DefaultIfEmpty()
     select new RestaurantViewModel
     {
        Id=r.Id,
        Name=r.Name,
        City=r.City,
        Country=r.Country,
        NumberofReviews=r.Reviews.Count,
        Reviews=rr.Body
     });

在进行一些更改之前，这个查询工作正常，然后我做了一些更改（我不记得了），然后开始发出此错误

错误图片



我的实体如下：

Before making some changes this query worked fine and then I made some changes (which I don't remember), then it started issuing this error
Error Image

My Entities are as follows:

public class Restaurant
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string City { get; set; }
    public string Country { get; set; }
    public virtual ICollection<RestaurantReview> Reviews { get; set; }
}

public class RestaurantReview
{
    public int Id { get; set; }
    public int Rating { get; set; }
    public string ReviewerName { get; set; }
    public string Body { get; set; }

    public int RestaurantId { get; set; }
}

public class RestaurantViewModel
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string City { get; set; }
    public string Country { get; set; }
    public int NumberofReviews { get; set; }
    public string Reviews { get; set; }    
}

请帮我解决这个错误。

谢谢

Please help me solve this error.
Thank you

推荐答案

EF不允许您将查询的复杂结果投影到映射的实体上。您可以使用不从映射实体继承的DTO或匿名类型。



尝试使用以下代码：

EF doesn't allow you to project the complex results of a query onto a mapped entity. You can do use a DTO or anonymous type which doesn't inherit from the mapped entity.

Try with below code:

var model = (from r in _db.Restaurants
     join rev in _db.Reviews
     on r.Id equals rev.RestaurantId
     into rest_rev
     from rr in rest_rev.DefaultIfEmpty())
     select new
     {
        Id=r.Id,
        Name=r.Name,
        City=r.City,
        Country=r.Country,
        NumberofReviews=r.Reviews.Count,
        Reviews=rr.Body
     }).ToList().Select(rec = > new RestaurantViewModel()
     {
        Id=rec.Id,
        Name=rec.Name,
        City=rec.City,
        Country=rec.Country,
        NumberofReviews=rec.Reviews.Count,
        Reviews=rec.Body
     });

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