使用SaveChangesAsync功能与非异步的WebAPI [英] Using SaveChangesAsync feature with non async webapi

问题描述

我有一定的WebAPI .NET编写mvc4和使用EF6，现在我所有的API控制器不是异步的，我想用EF6结果的SaveChangesAsync特点

I have some webapi written in .net mvc4 and using EF6 , now all my api controllers are not async , and i wanted to use SaveChangesAsync feature of EF6

我的API看起来类似结果

My api looks something like

public HttpResponseMessage Post(#some argument)
{
   ///so some computation and db operations without saving them

   // here i want to save all the db operations i had done above
   db.SaveChangesAsync();//Task 1

  // again do some computation 

  // wait for operation(Task1) to get complelte

  //do some computation

}

我如何可以利用EF6 SaveChangesAsync（）功能，而不用真正改变我的每个API控制器的异步到

How can i make use of EF6 SaveChangesAsync() feature without actually changing each of my api controller to async.

推荐答案

的 SaveChangesAsync 返回的 任务 ，所以你可以叫的 任务。等待（） 你需要确保它是完整的地步。你并不需要改变异步的方法，为了做到这一点。

SaveChangesAsync returns a Task, so you can just call Task.Wait() at the point you need to make sure it's complete. You don't need to change the method to async in order to do this.

public HttpResponseMessage Post(#some argument)
{
  Task saveTask = null;
  ///so some computation and db operations without saving them
  bool shouldSave1 = doCalcs(onState);

  if (shouldSave1) {
    // here i want to save all the db operations i had done above
    saveTask = db.SaveChangesAsync(); //Task 1
  }

  // again do some computation 

  if (shouldSave1) {
    // wait for operation(Task1) to get complete
    saveTask.Wait(); // this blocks until the task completes
  }

  //do some computation
}

脚注

这个答案只能说明你是如何做到这一点假设你需要。在这种特殊情况下（调用 SaveChangesAsync 直接在操作中），它会正常工作。它不讨论，如果你应该做的是：有很多情况下等待 ING在工作从异步返回方法将死锁 ApiController 操作的请求上下文。因此下面的code是不恰当的。请参见斯蒂芬·克利里：不要阻止异步code 一个例子。

Footnote

This answer only shows you how to do this assuming you need to. In this particular situation (calling SaveChangesAsync directly within the action) it will work. It does not discuss if you should do it: there are many situations where Waiting on the Task returned from an async method will deadlock the ApiController action's request context. The code below would therefore not be appropriate. See Stephen Cleary: Don't Block on Async Code for an example.

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