使用包含vs然后包含 [英] Using Include vs ThenInclude

问题描述

我一直在尝试使用EntityFramework，在遇到下面的错误之后，我尝试使用ThenInclude来解决它。

I have been experimenting a little with EntityFramework, and after facing the error bellow, i tried using ThenInclude to resolve it.

The传递给Include运算符的表达式'[x] .ModelA.ModelB'无法绑定

The expression '[x].ModelA.ModelB' passed to the Include operator could not be bound

但是现在看来我缺乏理解为何能解决问题

But now it seems i lack some understanding of why it did solve the problem

这有什么区别？

.Include(x => x.ModelA.ModelB)

这：

.Include(x => x.ModelA).ThenInclude(x => x.ModelB)

推荐答案

包含可以很好地与对象列表配合使用，但是如果需要获取多级数据那么 ThenInclude是最合适的。让我用一个例子来解释。假设我们有两个实体组织和客户，

"Include" work well with list of object but if need to get multi-level data then "ThenInclude" is the best fit. Let me explain it with an example. Say we have two entities Organization and Clients,

public class Company
{
    public string Name { get; set; }

    public string Location { get; set; }

    public List<Client> Clients {get;set;}
}

 public class Client
 {
    public string Name { get; set; }

    public string Domains { get; set; }

    public List<string> CountriesOfOperation { get; set; }
 }

现在，如果您只需要公司和该公司的整个客户列表，就可以只需使用包含，

Now if you want just companies and whole client list of that company you can just use "Include",

using (var context = new YourContext())
{
  var customers = context.Companies
    .Include(c => c.Clients)
    .ToList();
}

但是如果要将公司和 CountriesOfOperation作为相关数据，则可以在包含如下所示的客户端之后，使用 ThenInclude。

But if you want company and the "CountriesOfOperation" as related data then you can use "ThenInclude" after including Clients like below,

using (var context = new MyContext())
{
   var customers = context.Companies
    .Include(i => i.Clients)
      .ThenInclude(a => a.CountriesOfOperation)
    .ToList();
}

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