为什么我会收到此错误：远程服务器返回错误：（417）预期失败答案

【问题标题】：Why do I receive this error: The remote server returned an error: (417) Expectation Failed为什么我会收到此错误：远程服务器返回错误：（417）预期失败
【发布时间】：2012-06-14 00:36:35
【问题描述】：

一位朋友向我展示了在 C# 中实现 HTTP POST 的示例代码，并在 WINFORM 应用程序中运行： http://www.terminally-incoherent.com/blog/2008/05/05/send-a-https-post-request-with-c/

并在 METRO APP 中实现：

 // this is what we are sending
string post_data = "user=user@example.com&pass=example123";

// this is where we will send it
string uri = "http://app.proceso.com.mx/win8/login";

// create a request
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
request.Method = "POST";

// turn our request string into a byte stream
byte[] postBytes = Encoding.UTF8.GetBytes(post_data);

// this is important - make sure you specify type this way
request.ContentType = "application/x-www-form-urlencoded";
Stream requestStream = await request.GetRequestStreamAsync();

// now send it
requestStream.Write(postBytes, 0, postBytes.Length);

// grab te response and print it out to the console along with the status code
WebResponse response = await request.GetResponseAsync();
//var a = new StreamReader(response.GetResponseStream()).ReadToEnd();
StreamReader requestReader = new StreamReader(response.GetResponseStream());
String webResponse = requestReader.ReadToEnd();

我意识到，HttpWebRequest 不包含 ProtocolVersion 并在此行中向我抛出此错误：

WebResponse response = await request.GetResponseAsync();
// ERROR: The remote server returned an error: (417) Expectation Failed.

我猜最后一个属性是解决方案。我怎么解决这个问题？提前致谢

【问题讨论】：

尝试将以下内容放在顶部：ServicePointManager.Expect100Continue = false; 另外，您为什么使用异步版本的方法，然后使用await 阻塞，所有这些功能都有同步版本。跨度>

标签： c# httpwebrequest http-headers microsoft-metro

【解决方案1】：

我最近编写了一个小函数来处理将琐碎数据发布到服务器。

private struct HttpPostParam
{
    private string _key;
    private string _value;

    public string Key { get { return HttpUtility.UrlEncode(this._key); } set { this._key = value; } }
    public string Value { get { return HttpUtility.UrlEncode(this._value); } set { this._value = value; } }

    public HttpPostParam(string key, string value)
    {
        this._key = key;
        this._value = value;
    }
};

private static string PostTrivialData(Uri page, HttpPostParam[] parameters)
{
    string pageResponse = string.Empty;
    try
    {
        var request = (HttpWebRequest)WebRequest.Create(page); //create the initial request.
        request.Method = WebRequestMethods.Http.Post; //set the method
        request.AllowAutoRedirect = true; //couple of settings I personally prefer.
        request.KeepAlive = true;
        request.ContentType = "application/x-www-form-urlencoded";

        //create the post data.
        byte[] bData = Encoding.UTF8.GetBytes(string.Join("&", Array.ConvertAll(parameters, kvp => string.Format("{0}={1}", kvp.Key, kvp.Value))));
        using (var reqStream = request.GetRequestStream())
            reqStream.Write(bData, 0, bData.Length); //write the data to the request.

        using (var response = (HttpWebResponse)request.GetResponse()) //attempt to get the response.
            if (response.StatusCode == HttpStatusCode.OK || response.StatusCode == HttpStatusCode.NotModified) //check for a valid status (should only return 200 if successful)
                using (var reader = new System.IO.StreamReader(response.GetResponseStream()))
                    pageResponse = reader.ReadToEnd();
    }
    catch (Exception e)
    {
        /* todo: any error handling, for my use case failing gracefully was all that was needed. */
    }
    return pageResponse;
}

本质上，它发布“参数”参数中定义的值对。需要引用和导入 System.Web 命名空间才能编译。

我刚刚在您的网站上进行了测试并得到了回复：

HttpPostParam[] httpparams = {
                                new HttpPostParam("user", "censored@email.com"),
                                new HttpPostParam("pass", "example123")
                             };
string response = PostTrivialData(new Uri("http://app.proceso.com.mx/win8/login"), httpparams);

如果有任何问题，请告诉我。

【讨论】：