c# - Xamarin 上的 WebHeaderCollection 和 HttpWebRequest

Question

我正在尝试将我的项目从 Mac 上的 Xamarin Studio 移植到 Windows 7 上的 Visual Studio 2012。 在 Mac 和 XS 上一切正常。在 VisualStudio 2012 上，我遇到了这两个问题:

Error 3 'System.Net.WebHeaderCollection' does not contain a definition for 'Add' and no extension method 'Add' accepting a first argument of type 'System.Net.WebHeaderCollection' could be found (are you missing a using directive or an assembly reference?) C:\Users\user\Documents\Visual Studio 2012\Projects\MyProject\MyProject.Core\Services\MyProjectService.cs

Error 4 'System.Net.HttpWebRequest' does not contain a definition for 'GetResponse' and no extension method 'GetResponse' accepting a first argument of type 'System.Net.HttpWebRequest' could be found (are you missing a using directive or an assembly reference?) C:\Users\user\Documents\Visual Studio 2012\Projects\MyProject\MyProject.Core\Services\MyProjectService.cs

在该代码上:

    var request = WebRequest.Create("https://www.myaddress.com/test/") as HttpWebRequest;
    request.Method = "GET";
    request.Accept = "application/json";
    request.Headers.Add(HttpRequestHeader.Cookie,"mycookievalue");

    // Get response  
    using (var response = request.GetResponse() as HttpWebResponse)
    {
        // Get the response stream  
        var reader = new StreamReader(response.GetResponseStream());
        content = reader.ReadToEnd();
    }

我该如何解决？

Answer 1

到目前为止，您提到的事情没有实现。 但没关系。他们仍然做得很好!

回答您的问题。

错误 3。是的。目前您只能使用 Headers["key"] = value。但。不是每个标题。我试图将“Content-Length”放在那里(因为也没有实现“ContentLength”属性)，但出现“restricted headers”异常。 然而，请求 POST 为我成功处理，所以我放弃了。

错误 4。是的。没有这样的方法。 (同样的方式，因为没有“GetRequestStream”(例如，如果您要将 POST 数据写入请求流))。好消息是分别有 BeginGetResponse 和 BeginGetRequestStream，并且 C# action methods 简化了所有厨房。

(另外，我敢肯定，这对于异步实践的一般理解非常有用)。

可以在 Microsoft official docs 上找到基本示例.

但是我使用了以下操作来完成它:

    public void MakeRequest(string url, string verb, Dictionary<string, string> requestParams,
        Action<string> onSuccess, Action<Exception> onError)
    {
        string paramsFormatted;

        if (verb == "GET")
        {
            paramsFormatted = string.Join("&", requestParams.Select(x => x.Key + "=" + Uri.EscapeDataString(x.Value)));
            url = url + (string.IsNullOrEmpty(paramsFormatted) ? "" : "?" + paramsFormatted);
        }
        else
        {
            // I don't escape parameters here,
            // as Uri.EscapeDataString would throw exception if the parameter length
            // is too long, so you must control that manually before passing them here
            // for instance to convert to base64 safely
            paramsFormatted = string.Join("&", requestParams.Select(x => x.Key + "=" + (x.Value)));
        }

        var request = (HttpWebRequest)WebRequest.Create(url);
        request.Method = verb;

        requestParams = requestParams ?? new Dictionary<string, string>();

        Action goRequest = () => MakeRequest(request, 
            response =>
            {
                onSuccess(response);
            },
            error =>
            {
                if (onError != null)
                {
                    onError(error);
                }
            });

        if (request.Method == "POST")
        {
            request.BeginGetRequestStream(ar =>
            {
                using (Stream postStream = request.EndGetRequestStream(ar))
                {
                    byte[] byteArray = Encoding.UTF8.GetBytes(paramsFormatted);
                    postStream.Write(byteArray, 0, paramsFormatted.Length);
                }
                goRequest();
            }, request);
        }
        else // GET
        {
            goRequest();
        }
    }

    private void MakeRequest(HttpWebRequest request, Action<string> onSuccess, Action<Exception> onError)
    {
        request.BeginGetResponse(token =>
        {
            try
            {
                using (var response = request.EndGetResponse(token))
                {
                    using (var stream = response.GetResponseStream())
                    {
                        var reader = new StreamReader(stream);
                        onSuccess(reader.ReadToEnd());
                    }
                }
            }
            catch (WebException ex)
            {
                onError(ex);
            }
        }, null);
    }