如何使用存储库模式在 EF Core 3.0 中进行并行异步查询? [英] How to make parallel async queries in EF Core 3.0 with repository pattern?

问题描述

我有这样的仓库

public interface IEmployeeRepository
{
  Task<EmployeeSettings> GetEmployeeSettings(int employeeId);
  Task<ICollection<DepartmentWorkPosition>> GetWorkPositions(int employeeId);
}

存储库的构造函数(DbContext 注入):

Constructor of repository (DbContext injection):

public EmployeeRepository(EmployeeDbContext dbContext)
{
  _dbContext = dbContext;
}

并在 EF Core 2.0 中调用它

And call it in EF Core 2.0 like

var settingsTask = _employeeRepository
    .GetEmployeeSettings(employeeId.Value);

var workPositionsTask = _employeeRepository
    .GetWorkPositions(employeeId.Value);

await Task.WhenAll(settingsTask, workPositionsTask);

// do other things...

问题:

EF Core 3.0 存在 InvalidOperationException:在上一个操作完成之前，在此上下文上启动了第二个操作...

With EF Core 3.0 there is InvalidOperationException: a second operation started on this context before a previous operation completed...

DbContext 在 ConfigureServices 中注册，例如

DbContext is registered in ConfigureServices like

services.AddDbContext<EmployeeDbContext>(ServiceLifetime.Transient);

教程如下:Entity Framework Core 不支持在同一个 DbContext 实例上运行多个并行操作.

Tutorial says following: Entity Framework Core does not support multiple parallel operations being run on the same DbContext instance.

但是！如何在异步存储库中使用它?

But! How to use it with repositories in async?

推荐答案

如何在异步存储库中使用它?

How to use it with repositories in async?

每个存储库只能有一个并发异步请求.如果您需要一次拥有多个，那么您需要多个存储库.这可能需要您将存储库工厂注入您的类型.

You can only have one simultaneous asynchronous request per repository. If you need to have more than one at a time, then you need more than one repository. This may require you to inject a repository factory into your types.

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