如何使用存储库模式在 EF Core 3.0 中进行并行异步查询?

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

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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