Question

我正在尝试使用HttpClient类获取/发布并面临以下问题

不知道如何从HttpResponseMessage.Content.ReadAsStringAsync（）。ContinueWith（）方法返回任务。

出于某种原因，它会继续自动取消

    private static Task<T> HttpClientSendAsync<T>(string url, object data, HttpMethod method, string contentType, CancellationToken token)
{
    HttpRequestMessage httpRequestMessage = new HttpRequestMessage(method, url);
    RetryDelegatingHandler retryDelegatingHandler = new RetryDelegatingHandler();
    retryDelegatingHandler.PreAuthenticate = true;
    retryDelegatingHandler.Credentials = Credential;
    retryDelegatingHandler.Proxy = null;

    HttpClient httpClient = new HttpClient(retryDelegatingHandler);
    httpClient.Timeout = new TimeSpan(Constants.TimeOut);

    if (data != null)
    {
        byte[] byteArray = Encoding.ASCII.GetBytes(Helper.ToJSON(data));
        MemoryStream memoryStream = new MemoryStream(byteArray);
        httpRequestMessage.Content = new StringContent(new StreamReader(memoryStream).ReadToEnd(), Encoding.UTF8, contentType);
    }

    Task<HttpResponseMessage> httpResponseMessage = httpClient.SendAsync(httpRequestMessage);
    httpResponseMessage.ContinueWith((task) =>
        {
            if (!task.IsFaulted)
            {
                HttpResponseMessage response = task.Result;
                response.Content.ReadAsStringAsync().ContinueWith(
                (stringTask) =>
                {
                    if (!stringTask.IsFaulted)
                    {
                        return Helper.FromJSON<T>(stringTask.Result);
                    }
                    else
                    {
                        Logger.Log(string.Format("SendAsyncRequest Task IsFaulted: {0} \nException: {1}", typeof(T), task.Exception));
                        UpdateError(typeof(T).ToString());

                        return default(T);
                    }
                });
            }
            else
            {
                Logger.Log(string.Format("SendAsyncRequest Task IsFaulted: {0} \nException: {1}", typeof(T), task.Exception));
                UpdateError(typeof(T).ToString());

                return default(T);
            }
        });
}

更新：它确实有效，但在尝试处理故障时它仍无法正常工作。

    return httpClient.SendAsync(httpRequestMessage).ContinueWith(task =>
    {
        var response = task.Result;
        return response.Content.ReadAsStringAsync().ContinueWith(stringTask =>
        {
            var json = stringTask.Result;
            return Helper.FromJSON<T>(json);
        });
    }).Unwrap();

Answer 1

Task.ContinueWith返回继续任务：Task或Task<T>。如果我理解这个问题，在这种情况下你可以这样做：

var continuation = httpResponseMessage.ContinueWith((task) =>
    {
        if (!task.IsFaulted)
        {
            HttpResponseMessage response = task.Result;
            return response.Content.ReadAsStringAsync().ContinueWith(
            (stringTask) =>
            {

            ...

和continuation最终会成为Task<Task<T>>，您可以致电.Unwrap()将其转换为代理任务Task<T>。

如何从HttpResponseMessage.Content.ReadAsStringAsync（）返回Task <t>。ContinueWith（）方法？</t>

1 个答案: