windows-phone-8 - “System.Net.HttpWebRequest”不包含 'GetResponse' 的定义

Question

我正在使用框架 4.5 在 Visual Studio 2013 中创建一个使用 Restful GET 方法的方法。这是 windows_phone_8(针对 Phone OS 8.0)应用程序。这是我的代码。

static string HttpGet(string url)
    {
        HttpWebRequest req = WebRequest.Create(url)
                             as HttpWebRequest;
        string result = null;
        using (HttpWebResponse resp = req.GetResponse()
                                      as HttpWebResponse)
        {
            StreamReader reader =
                new StreamReader(resp.GetResponseStream());
            result = reader.ReadToEnd();
        }
        return result;
    }

但我收到如下构建错误

'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?)

我不知道为什么会发生这种情况，相同的代码在相同的环境中与 Windows_application 一起正常工作。

更新:我也尝试过使用 Web 客户端方法

 WebClient client = new WebClient();

            client.Headers.Add("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");

            Stream data = client.OpenRead("http://192.168.10.73:8087/cisms/mobilews/login/userNameCheck?userName=supervisor");
            StreamReader reader = new StreamReader(data);
            string s = reader.ReadToEnd();
            data.Close();
            reader.Close();

得到另一组错误...

Error 1 '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?)

Error 2 'System.Net.WebClient' does not contain a definition for 'OpenRead' and no extension method 'OpenRead' accepting a first argument of type 'System.Net.WebClient' could be found (are you missing a using directive or an assembly reference?)

Error 3 '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?)

更新 2:

我根据@Gavin 的回答更改了代码如下。

static async void HttpGet(string url)
    {
        Uri uri = new Uri(url);
        string result = null;
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
        request.Method = "GET";
        using (var response = (HttpWebResponse)(await Task<WebResponse>.Factory.FromAsync(request.BeginGetResponse, request.EndGetResponse, null)))
        {
            StreamReader reader = new StreamReader(response.GetResponseStream());
            result = reader.ReadToEnd();
        }
    }

但是控制返回到调用事件，从以下行

using (var response = (HttpWebResponse)(await Task<WebResponse>.Factory.FromAsync(request.BeginGetResponse, request.EndGetResponse, null)))

对此的任何帮助将不胜感激。

答案:

我按如下方式更改了代码，现在可以正常工作了..

public async Task<string> httpRequest(string url)
        {
            Uri uri = new Uri(url);
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
            string received;

            using (var response = (HttpWebResponse)(await Task<WebResponse>.Factory.FromAsync(request.BeginGetResponse, request.EndGetResponse, null)))
            {
                using (var responseStream = response.GetResponseStream())
                {
                    using (var sr = new StreamReader(responseStream))
                    {

                        received = await sr.ReadToEndAsync();
                    }
                }
            }

            return received;
        }

调用部分如下...

private async void Button_Click(object sender, RoutedEventArgs e)
        {
            string uriString = "http://192.168.10.73:8087/cisms/mobilews/login/userNameCheck?userName=supervisor";
            var response = await httpRequest(uriString);
        }

更新 3:

我在处理 POST 请求时还有一个问题。我试过的代码如下。

static string HttpPost(string url, string[] paramName, string[] paramVal)
        {
            HttpWebRequest req = WebRequest.Create(new Uri(url))
                                 as HttpWebRequest;
            req.Method = "POST";
            req.ContentType = "application/x-www-form-urlencoded";

            // Build a string with all the params, properly encoded.
            // We assume that the arrays paramName and paramVal are
            // of equal length:
            StringBuilder paramz = new StringBuilder();
            for (int i = 0; i < paramName.Length; i++)
            {
                paramz.Append(paramName[i]);
                paramz.Append("=");
                paramz.Append(HttpUtility.UrlEncode(paramVal[i]));
                paramz.Append("&");
            }

            // Encode the parameters as form data:
            byte[] formData =
                UTF8Encoding.UTF8.GetBytes(paramz.ToString());
            req.ContentLength = formData.Length;

            // Send the request:
            using (Stream post = req.GetRequestStream())
            {
                post.Write(formData, 0, formData.Length);
            }

            // Pick up the response:
            string result = null;
            using (HttpWebResponse resp = req.GetResponse()
                                          as HttpWebResponse)
            {
                StreamReader reader =
                    new StreamReader(resp.GetResponseStream());
                result = reader.ReadToEnd();
            }

            return result;
        }

此方法在 Windows 手机 8 应用程序中有两个构建错误

Error 1 'System.Net.HttpWebRequest' does not contain a definition for 'GetRequestStream' and no extension method 'GetRequestStream' accepting a first argument of type 'System.Net.HttpWebRequest' could be found (are you missing a using directive or an assembly reference?)

Error 2 '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?)

谢谢
塞巴斯蒂安

Answer 1

WP8 支持 .NET Framework 4.5 的一个子集。

您可以根据需要调整以下代码变体:

WebRequest request = WebRequest.Create(url);
return Task.Factory.FromAsync(request.BeginGetResponse, result =>
{
    HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(result);
    ...
}

或者

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
request.Method = "GET";
using (var response = (HttpWebResponse)(await Task<WebResponse>.Factory.FromAsync(request.BeginGetResponse, request.EndGetResponse, null)))
{
    ...
}