System.ArgumentException:标头具有空值

Question

我得到一个例外,因为"标题有一个空值".这是POST请求.在某些情况下,我需要将一些标头值发送为空.

这是我的代码:

private void Start()
{
    try
    {
        this.webRequest = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(this.requestURL);
        //this.webRequest.Headers[HttpRequestHeader.UserAgent] = this.userAgent;
        webRequest.Headers[HttpRequestHeader.CacheControl] = "no-cache";
        webRequest.Headers[HttpRequestHeader.Pragma] = "no-cache";
        webRequest.Headers[HttpRequestHeader.IfModifiedSince] = DateTime.UtcNow.ToString();
        webRequest.Method = "POST";

        if (headers != null && headers.Count > 0)
        {
            webRequest.Headers["some-Header"] = ""; 
        }

        IAsyncResult result = this.webRequest.BeginGetRequestStream(new AsyncCallback(RequestCallback), webRequest);
    }
    catch (Exception ex)
    {
    }
}

void RequestCallback(IAsyncResult result)
{
    HttpWebRequest request = (HttpWebRequest)result.AsyncState;

    //if (RequestBody != null)
    {
        using (Stream postStream = request.EndGetRequestStream(result))
        {
            using (var writer = new StreamWriter(postStream))
            {
                writer.Write(string.Empty);
                writer.Flush();
                postStream.Position = 0;
                byte[] mArray = new byte[postStream.Length];
                postStream.Read(mArray, 0, (int)postStream.Length);
            }
        }
    }

    request.BeginGetResponse(new AsyncCallback(OnRequestResponse), request);
}

private void OnRequestResponse(IAsyncResult ar)
{
    try
    {
        System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)this.webRequest.EndGetResponse(ar);
        webResponseHeaders = response.Headers.GetHeaders();
        System.IO.Stream responseStream = response.GetResponseStream();
    }
    catch (Exception ex)
    {
    }
}

在System.Net.HttpWebResponse的OnRequestResponse回调中获取异常response =(System.Net.HttpWebResponse)this.webRequest.EndGetResponse(ar);

Answer 1

首先，尝试将您的解决方案升级到 Windows Phone 8.1 有 2 个选项：Silverlight 8.1（您可以重用所有代码）或 WP 8.1 RT（轻松在 WP 和 Windows 8.1 之间重用代码）。我建议使用 Silverlight 8.1，因为您已经有正在开发的 Silverlight 8.0 应用程序。

第二件事：回调有点旧了。考虑将代码升级为 Await 和 Async 方法，因为它自然受支持

对于您的问题，请尝试使用 HttpClient 发送请求。这里是一个代码示例：

public static async Task<string> GetHttpAsStringTask(string uriString)
    {
        string result;

        Uri targetUri = new Uri(uriString);

        HttpClient client = new HttpClient();
        HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, targetUri);
        //Add your empty header here
        request.Headers.Add("Header name","header value");
        HttpResponseMessage response = await client.SendAsync(request);

        using (Stream responseStream = await response.Content.ReadAsStreamAsync())
        {
            StreamReader reader = new StreamReader(responseStream, Encoding.UTF8);
            result = reader.ReadToEnd();
        }

        return result;
    }

用法：

string response = await GetHttpAsStringTask("your url");

对于 WP 8 中的等待和异步：http://developer.nokia.com/community/wiki/Asynchronous_Programming_For_Windows_Phone_8