Question

我在这里有以下情况。如何在DB调用异步运行时进行一些并行处理。

/// <summary>
    /// Async query EF6.0
    /// </summary>
    /// <returns></returns>
    public async Task<ActionResult> AsyncQuery()
    {
        var result = await GetAsyncDepartments();
        Debug.WriteLine("Do some stuff here");

        return View("Index");
    }

    private async Task<List<Department>> GetAsyncDepartments()
    {
        var depts = new List<Department>();
        using (var newContext = new DemoEntities())
        {
            depts = await newContext.Departments.ToListAsync();
        }
        Debug.WriteLine("Got departments");
        return depts;
    }

它实际上等待任务完成，然后转到语句“在这里做一些事情”。

如何异步调用GetAsyncDepartments（）并执行一些额外的操作直到调用返回。谢谢。

Answer 1

GetAsyncDepartments将返回Task的实例，您可以＆＃34;等待＆＃34;在＆＃34;一些员工＆＃34;将被执行。

public async Task<ActionResult> AsyncQuery()
{
    var task = GetAsyncDepartments();
    Debug.WriteLine("Do some stuff here");

    await task;
    return View("Index");
}

Answer 2

await要求您的代码等待电话。您可以在需要时拨打GetAsyncDepartments，但只能await。例如：

async Task Main()
{
    var finalResult = await AsyncQuery();
    Console.WriteLine(finalResult);
}

public async Task<int> AsyncQuery()
{
    var result = GetAsyncDepartments();
    Debug.WriteLine("Do some stuff here");
    return await result;
}

public async Task<int> GetAsyncDepartments()
{
    Console.WriteLine("Starting GetAsyncDepartments");
    await Task.Delay(5000);
    Console.WriteLine("Finished GetAsyncDepartments");
    return 5;
}

产生输出：

启动GetAsyncDepartments
  在这里做一些事情   完成GetAsyncDepartments
  5

如何在MVC4中执行异步调用操作方法

2 个答案: