使用 Entity Framework 的即时加载时 ASP NET Core 崩溃

Question

我有一个简单的电话：

 public IActionResult GetApplications()
 {
        var result = context.Applications.Include(a=> a.AplicantCompany)
            .Include(c=>c.CreditorCompany)
            .ToList();
        return Ok(result);
 }

返回：

{"result":[{"context":null,"applicationId":1003,"aplicantCompany":{"id":1,"creditCompid":12344,"name":"Kibon","industry":"ice cream","address":"RaiboW street","city":"Rio de Janeiro","province":"Rio de Janeiro","country":"Brazil","postalCode":"9034-394","style":"modern","yearsStablished":100,"numEmployees":600,"salesAnnual":"12343434","taxId":323,"functionOfScore":12,"dateCreated":"2018-08-09T14:14:38.3325627"},"applicantCompanyID":1,"creditRequested":33333,"creditTerm":1,"processStatus":1,"recommendation":1,"approved":true,"creditApproved":1200000,"dateCreated":"2018-08-09T14:18:32.900369","dateProcessed":"2018-12-12T00:00:00","creditorCompanyId":1,"creditorCompany":{"creditorCompanyId":1,"name":"IBM","address":"boulevard of dreams","city":"Toronto","province":"ON","country":"Canada","postalCode":"M1t 2t5","revenue":12343,"riskPreference":23,"creditLimit":123,"portofolioScore":5.5,"userName":"Ronald","password":"1234","dateCreated":"2018-08-09T12:09:18.0977008","applications":[

由于某种原因，Entity 在获取其余数据之前就崩溃了。

当我尝试使用属性时：

[HttpGet("/api/applications")]
public IActionResult GetApplications()
{
    var result = context.Applications.Include(a=> a.AplicantCompany.Name)
                .Include(c=>c.CreditorCompany.Name)
                .ToListAsync();
    return Ok(result);
}

我没有收到任何东西。有人知道发生了什么吗？

注意：我现在收到此错误：

System.InvalidOperationException：“属性“名称”不是实体类型“ApplicantCompany”的导航属性。 'Include(string)' 方法只能与 '.' 一起使用。导航属性名称的分隔列表。'

但是属性存在...

Answer 1

您对ToListAsync() 的调用返回一个Task，在您从该方法返回时，它可能尚未完成执行。最好的解决方案是使方法异步，如下所示：

public async Task<IActionResult> GetApplications()
{
   var result = await context.Applications.Include(a=> a.AplicantCompany)
      .Include(c=>c.CreditorCompany)
      .ToListAsync();
   return Ok(result);
}

这些更改将导致该方法在继续执行return 语句之前等待所有结果，同时允许其他请求在此等待其数据时运行。

第二种情况可能行不通，因为 EF 想用Include 加载整个实体。如果要加载AplicantCompany 引用的另一个实体，可以使用

.Include(a => a.AplicantCompany).ThenInclude(c => c.Entity)

其实按照this answer，你或许可以做到（我没试过）：

var result = await context.Applications.Select(a => new {
    Application = a,
    CreditorCompany = a.CreditorCompany.Name,
    ApplicantCompany = a.AplicantCompany.Name}).ToListAsync();

Answer 2

首先，

Include() 方法用于加载相关数据，而不是相关数据的属性。 这意味着，要在实体 Applications 上加载相关 AplicantCompany 和 CreditorCompany 的 name 属性，您的第一个查询是正确的。 它将包括两个相关实体的名称属性

var result = context.Applications.Include(a=> a.AplicantCompany)
                .Include(c=>c.CreditorCompany)
                .ToList();

其次，如果你使用的是异步方法 ToListAsync() 你需要等待任务

[HttpGet("/api/applications")]
public async Task<IActionResult> GetApplications()
{
    var result = await context.Applications.Include(a=> a.AplicantCompany)
                .Include(c=>c.CreditorCompany)
                .ToListAsync();
    return Ok(result);
}

Answer 3

您对ToListAsync 的调用是异步的；但是调用和方法本身是同步的。更改为 ToList() 或（更好）使其他所有内容也异步