相关疑难解决方法(0)

我有一个SQL Server数据库,表中有500,000条记录main.还有其他三个表叫child1,child2和child3.很多之间一对多的关系child1,child2,child3,并main通过三个关系表来实现:main_child1_relationship,main_child2_relationship,和main_child3_relationship.我需要读取记录main,更新main,并在关系表中插入新行以及在子表中插入新记录.子表中的记录具有唯一性约束,因此实际计算的伪代码(CalculateDetails)将类似于:

for each record in main
{
   find its child1 like qualities
   for each one of its child1 qualities
   {
      find the record in child1 that matches that quality
      if found
      {
          add a record to main_child1_relationship to connect the two records
      }
      else
      {
          create a new record in child1 for the …

我有像

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）：

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

并在 EF Core 2.0 中调用它，例如

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

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

await Task.WhenAll(settingsTask, workPositionsTask);

// do other things...

问题：

对于 EF Core 3.0，有 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...

DbContext 在 ConfigureServices 中注册，如

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。

但！如何在异步存储库中使用它？