c# - 在不阻塞 UI 线程的情况下异步使用 HttpWebRequest

Question

我正在尝试在 WinForms 应用程序中异步使用 HttpWebRequest 和 HttpWebResonse 而不阻塞我的 UI 线程。

我看到了这个similar SO Question这解释了如何去做。但是，我不是 100% 确定接受的答案是正确的方法。接受的答案是使用 BeginGetResponse。

根据MSDN documentation :

The BeginGetResponse method requires some synchronous setup tasks to complete (DNS resolution, proxy detection, and TCP socket connection, for example) before this method becomes asynchronous. As a result, this method should never be called on a user interface (UI) thread because it might take some time, typically several seconds.

谁能给我提供正确的方法来做到这一点。这是我试图在不阻塞 UI 线程的情况下“正常”工作的 C# 函数:

    private IDictionary<string, object> CreateWebRequest(string endPoint, string method, string data, bool addAuthHeader)
    {
        var req = (HttpWebRequest)WebRequest.Create(endPoint);
        req.Method = method;
        if (addAuthHeader)
        {
            req.Headers.Add(HttpRequestHeader.Authorization, "Bearer " + _accessToken.AccessToken);
        }

        if (!string.IsNullOrEmpty(data))
        {
            var utfenc = new UTF8Encoding();
            byte[] buffer = utfenc.GetBytes(data);
            req.ContentLength = buffer.Length;
            req.ContentType = "application/x-www-form-urlencoded";

            using (Stream strm = req.GetRequestStream())
            {
                strm.Write(buffer, 0, buffer.Length);
                strm.Close();
            }
        }

        HttpWebResponse response = null;
        try
        {
            response = (HttpWebResponse)req.GetResponse();
        }
        catch (WebException e)
        {
            if (_accessToken == null)
            {
                throw;
            }
            var responseError = (HttpWebResponse)e.Response;
            if (responseError.StatusCode == HttpStatusCode.Unauthorized)
            {
                var stackTrace = new StackTrace();
                var q = stackTrace.GetFrame(1).GetMethod().Name;
                RefreshAccessCode();

                req = (HttpWebRequest)WebRequest.Create(endPoint);
                req.Method = method;
                if (addAuthHeader)
                {
                    req.Headers.Add(HttpRequestHeader.Authorization, "Bearer " + _accessToken.AccessToken);
                }
                response = (HttpWebResponse)req.GetResponse();
            }
        }

        string jsonResponse = null;

        if (response != null)
            using (Stream stream = response.GetResponseStream())
            {
                if (stream != null)
                {
                    using (var reader = new StreamReader(stream))
                    {
                        jsonResponse = reader.ReadToEnd();
                    }
                }
            }

        return DeserializeResponse(jsonResponse);
    }

Answer 1

如果您对 WebRequest 以外的东西持开放态度，我是 System.Net.WebClient 的粉丝.它使用 System.Threading.Tasks 而不是 BeginGetResponse() 和 EndGetResonse()。

public async Task<Dictionary<string, object>> CreateWebRequest(string endPoint, string method, string data, bool addAuthHeader)
{
    WebClient client = new WebClient();

    if (addAuthHeader)
    {
        client.Headers.Add(HttpRequestHeader.Authorization, "Bearer " + _accessToken.AccessToken);
    }

    byte[] buffer = null;

    if (!string.IsNullOrEmpty(data))
    {
        var utfenc = new UTF8Encoding();
        buffer = utfenc.GetBytes(data);
    }
    else
    {
        buffer = new byte[0];
    }

    return await client.UploadDataTaskAsync(endPoint, method, buffer)
        .ContinueWith((bytes) =>
            {
                string jsonResponse = null;

                using (var reader = new StreamReader(new MemoryStream(bytes)))
                {
                    jsonResponse = reader.ReadToEnd();
                }

                return DeserializeResponse(jsonResponse);
            });
    }
}