Task.Factory.FromAsync与End方法中的"out"参数

Question

如何使用Task.Factory.FromAsync工厂为通过"out"参数返回多个值的end方法？

begin方法有这个签名:

public virtual System.IAsyncResult BeginGetCaseStatus(int CaseOID, int ClientOID, System.AsyncCallback @__Callback, object @__UserData)

结束方法是:

public virtual void EndGetCaseStatus(System.IAsyncResult @__AsyncResult, out DTGenericCode[] BasicStatus, out DTGenericCode[] ARStatus)

我可以用一些如何使用:

public Task<?> GetCaseStatusAsync(int CaseOID, int ClientOID)
{
    return Task.Factory.FromAsync  (BeginGetCaseStatus(CaseOID, ClientOID, null, null), EndGetCaseStatus(?, ?));
}

Answer 1

没有任何FromAsync重载可以解决这个问题.最好的选择可能是构建自己的包装器:

public class ResultStatus
{
     public ResultStatus(DTGenericCode[] basicStatus, DTGenericCode[] arStatus)
     {
         this.BasicStatus = basicStatus;
         this.ARStatus = arStatus;
     }
     public DTGenericCode[] BasicStatus { get; private set; }
     public DTGenericCode[] ARStatus { get; private set; }
}

public Task<ResultStatus> GetCaseStatusAsync(int CaseOID, int ClientOID)
{
     var tcs = new TaskCompletionSource<ResultStatus>();
     theClass.BeginGetCaseStatus(CaseOID, ClientOID, iar =>
             {
                 DTGenericCode[] bs;
                 DTGenericCode[] as;
                 theClass.EndGetCaseStatus(iar, out bs, out as);

                 tcs.SetResult(new ResultStatus(bs, as));
             }, null);

     return tcs.Task;
}

Answer 2

该endMethod参数FromAsync()是一个委托,所以你可以使用lambda的转换out-型到正常形态-End的方法.就像是:

private static Task<Tuple<DTGenericCode[], DTGenericCode[]>> GetCaseStatusAsync(
    int CaseOID, int ClientOID)
{
    return Task.Factory.FromAsync(
        BeginGetCaseStatus, ar =>
        {
            DTGenericCode[] basicStatus;
            DTGenericCode[] arStatus;

            EndGetCaseStatus(ar, out basicStatus, out arStatus);

            return Tuple.Create(basicStatus, arStatus);
        },
        CaseOID, ClientOID, null);
}

虽然您可能想要使用自定义类型而不是Tuple.