c# - 调试时异步行为同步？

Question

我对 async/await 的理解肯定存在缺陷。我想要一段名为 SaveSearchCase 的代码在后台异步运行。

我希望它被触发并忘记它并继续当前方法的 return 语句。

public IList<Entities.Case.CreateCaseOutput> createCase(ARC.Donor.Data.Entities.Case.CreateCaseInput CreateCaseInput, ARC.Donor.Data.Entities.Case.SaveCaseSearchInput SaveCaseSearchInput)
{
    ..........
    ..........
    ..........
    var AcctLst = rep.ExecuteStoredProcedure<Entities.Case.CreateCaseOutput>(strSPQuery, listParam).ToList();

    if (!string.IsNullOrEmpty(AcctLst.ElementAt(0).o_case_seq.ToString()))
    {
        Task<IList<Entities.Case.SaveCaseSearchOutput>> task = saveCaseSearch(SaveCaseSearchInput, AcctLst.ElementAt(0).o_case_seq);
        Task t = task.ContinueWith(
                r => { Console.WriteLine(r.Result); }
         );
    }
    Console.WriteLine("After the async call");
    return AcctLst;
}

SaveCaseSearch 看起来像

public async Task<IList<Entities.Case.SaveCaseSearchOutput>> saveCaseSearch(ARC.Donor.Data.Entities.Case.SaveCaseSearchInput SaveCaseSearchInput,Int64? case_key)
{
    Repository rep = new Repository();
    string strSPQuery = string.Empty;
    List<object> listParam = new List<object>();
    SQL.CaseSQL.getSaveCaseSearchParameters(SaveCaseSearchInput, case_key,out strSPQuery, out listParam);
    var AcctLst = await rep.ExecuteStoredProcedureAsync<Entities.Case.SaveCaseSearchOutput>(strSPQuery, listParam);
    return (System.Collections.Generic.IList<ARC.Donor.Data.Entities.Case.SaveCaseSearchOutput>)AcctLst;
}

但是当我看到调试器的 createCase 方法首先等待 SaveCaseSearch 完成，然后才完成

它打印“After Async Call”

然后返回。我绝对不想要。

那么我的理解在哪方面有缺陷？请帮助使其异步运行并继续当前方法的打印和返回语句。

更新

我更新了 SaveCaseSearch 方法以反射(reflect)如下:

public async Task<IList<Entities.Case.SaveCaseSearchOutput>> saveCaseSearch(ARC.Donor.Data.Entities.Case.SaveCaseSearchInput SaveCaseSearchInput,Int64? case_key)
{
    return Task.Run<IList<Entities.Case.SaveCaseSearchOutput>>(async (SaveCaseSearchInput, case_key) =>
    {
        Repository rep = new Repository();
        string strSPQuery = string.Empty;
        List<object> listParam = new List<object>();
        SQL.CaseSQL.getSaveCaseSearchParameters(SaveCaseSearchInput, case_key, out strSPQuery, out listParam);
        var AcctLst = await rep.ExecuteStoredProcedureAsync<Entities.Case.SaveCaseSearchOutput>(strSPQuery, listParam);
        return (System.Collections.Generic.IList<ARC.Donor.Data.Entities.Case.SaveCaseSearchOutput>)AcctLst;
    });
}

但是参数有问题。它说

Error   4   A local variable named 'SaveCaseSearchInput' cannot be declared in this scope because it would give a different meaning to 'SaveCaseSearchInput', which is already used in a 'parent or current' scope to denote something else C:\Users\m1034699\Desktop\Stuart_V2_12042016\Stuart Web Service\ARC.Donor.Data\Case\Search.cs   43  79  ARC.Donor.Data

Answer 1

saveCaseSearch() 方法在主线程中同步运行，这是这里的主要问题。与其返回带有任务的结果，不如返回带有操作本身的任务。这是一些简化的示例:

Runs synchronously and waits 5 seconds

    public IList<int> A()
    {

        var AcctLst = new List<int> { 0, 2, 5, 8 };

        if (true)
        {
            Task<IList<int>> task = saveCaseSearch();

            Task t = task.ContinueWith(
                    r => { Console.WriteLine(r.Result[0]); }
             );
        }

        Console.WriteLine("After the async call");

        return AcctLst;
    }

    // runs sync and in the end returns Task that is never actually fired
    public async Task<IList<int>> saveCaseSearch()
    {
        Thread.Sleep(5000);
        return new List<int>() { 10, 12, 16 };
    }

Runs asynchronously - fires task & forgets :

    public IList<int> A()
    {
        ... same code as above
    }

    // notice that we removed `async` keyword here because we just return task.
    public Task<IList<int>> saveCaseSearch()
    {
        return Task.Run<IList<int>>(() =>
        {
            Thread.Sleep(5000);
            return new List<int>() { 10, 12, 16 };
        });
    }

这里是 full code for this example