带有进度跟踪的 C# HttpWebRequest 表单发布(用于上传可能较大的文件)

Question

我有一个正在编写的 winforms 应用程序，它可以将文件发布到 Web 应用程序(不是我的)。就发布文件本身而言，我的工作一切正常，我的问题是我想提供一些指示，说明我在发送请求方面走了多远。

下面的代码是我为此目的使用 BeginGetResponse 的尝试 - 这是我发现请求仍然阻塞的地方。

关于我可以从哪里开始寻找的任何建议？

    public void Dummy()
    {
        Dictionary<string, string> fields = new Dictionary<string, string>();
        fields.Add("key", "something");

        HttpWebRequest hr = WebRequest.Create("http://somesite.com/api/something.xml") as HttpWebRequest;
        string bound = "----------------------------" + DateTime.Now.Ticks.ToString("x");
        hr.ContentType = "multipart/form-data; boundary=" + bound;
        hr.Method = "POST";
        hr.KeepAlive = true;
        hr.Credentials = CredentialCache.DefaultCredentials;

        byte[] boundBytes = Encoding.ASCII.GetBytes("\r\n--" + bound + "\r\n");
        string formDataTemplate = "\r\n--" + bound + "\r\nContent-Disposition: form-data; name=\"{0}\";\r\n\r\n{1}";

        Stream s = hr.GetRequestStream();

        foreach (string key in fields.Keys)
        {
            byte[] formItemBytes = Encoding.UTF8.GetBytes(
                string.Format(formDataTemplate, key, fields[key]));
            s.Write(formItemBytes, 0, formItemBytes.Length);
        }

        s.Write(boundBytes, 0, boundBytes.Length);

        string headerTemplate = 
            "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\n Content-Type: application/octet-stream\r\n\r\n";

        List<string> files = new List<string> { Server.MapPath("/Images/Phillip.jpg") };

        foreach (string f in files)
        {
            byte[] headerBytes = Encoding.UTF8.GetBytes(
                String.Format(headerTemplate, "image", f));

            s.Write(headerBytes, 0, headerBytes.Length);
            FileStream fs = new FileStream(f, FileMode.Open, FileAccess.Read);
            int bytesRead = 0;
            byte[] buffer = new byte[1024];
            while ((bytesRead = fs.Read(buffer, 0, buffer.Length)) != 0)
            {
                s.Write(buffer, 0, buffer.Length);
            }

            s.Write(boundBytes, 0, boundBytes.Length);
            fs.Close();
        }

        s.Close();

        string respString ="";
        hr.BeginGetResponse((IAsyncResult res) =>
            {
                WebResponse resp = ((HttpWebRequest)res.AsyncState).EndGetResponse(res);

                StreamReader respReader = new StreamReader(resp.GetResponseStream());
                respString = respReader.ReadToEnd();
                resp.Close();
                resp = null;
            }, hr);

        while (!hr.HaveResponse)
        {
            Debug.Write("hiya bob!");
            Thread.Sleep(150);
        }

        Debug.Write(respString);
        hr = null;
    }

Answer 1

好的，明白了。 HttpWebRequest 对象，如果您设置 ContentLength 属性，将在您调用 GetRequestStream() 时将其 ResponseStream 直接连接到网络套接字。然后，您可以通过直接写入此流来跟踪您的进度。

伪代码:

Request r = CreateWebRequest(Url)
r.ContentLength = CalculateRequestLength(fields, files)
Stream requestStream = r.GetRequestStream()
while(moreData)
{
  requestStream.write(someData);
  UpdateProgress();
}
r.GetResponse();

工作代码:

   public void Dummy()
    {
        Dictionary<string, string> fields = new Dictionary<string, string>();
        fields.Add("key", "something");

        HttpWebRequest hr = WebRequest.Create("http://imgur.com/api/upload.xml") as HttpWebRequest;
        string bound = "----------------------------" + DateTime.Now.Ticks.ToString("x");
        hr.ContentType = "multipart/form-data; boundary=" + bound;
        hr.Method = "POST";
        hr.KeepAlive = true;
        hr.Credentials = CredentialCache.DefaultCredentials;

        byte[] boundBytes = Encoding.ASCII.GetBytes("\r\n--" + bound + "\r\n");
        string formDataTemplate = "\r\n--" + bound + "\r\nContent-Disposition: form-data; name=\"{0}\";\r\n\r\n{1}";

        //add fields + a boundary
        MemoryStream fieldData = new MemoryStream();
        foreach (string key in fields.Keys)
        {
            byte[] formItemBytes = Encoding.UTF8.GetBytes(
                string.Format(formDataTemplate, key, fields[key]));
            fieldData.Write(formItemBytes, 0, formItemBytes.Length);
        }
        fieldData.Write(boundBytes, 0, boundBytes.Length);

        //calculate the total length we expect to send
        List<string> files = new List<string> { Server.MapPath("/Images/Phillip.jpg") };
        string headerTemplate =
            "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\n Content-Type: application/octet-stream\r\n\r\n";
        long fileBytes = 0;
        foreach (string f in files)
        {
            byte[] headerBytes = Encoding.UTF8.GetBytes(
                String.Format(headerTemplate, "image", f));
            FileStream fs = new FileStream(f, FileMode.Open, FileAccess.Read);

            fileBytes += headerBytes.Length;
            fileBytes += fs.Length;
            fileBytes += boundBytes.Length;
            fs.Close();
        }

        hr.ContentLength = fieldData.Length + fileBytes;

        Stream s = hr.GetRequestStream();           
        //write the fields to the request stream
        Debug.WriteLine("sending field data");
        fieldData.WriteTo(s);

        //write the files to the request stream
        Debug.WriteLine("sending file data");
        foreach (string f in files)
        {
            byte[] headerBytes = Encoding.UTF8.GetBytes(
                String.Format(headerTemplate, "image", f));
            s.Write(headerBytes, 0, headerBytes.Length);

            FileStream fs = new FileStream(f, FileMode.Open, FileAccess.Read);
            int bytesRead = 0;
            long bytesSoFar = 0;
            byte[] buffer = new byte[10240];
            while ((bytesRead = fs.Read(buffer, 0, buffer.Length)) != 0)
            {
                bytesSoFar += bytesRead;
                s.Write(buffer, 0, bytesRead);
                Debug.WriteLine(String.Format("sending file data {0:0.000}%", (bytesSoFar * 100.0f) / fs.Length));
            }

            s.Write(boundBytes, 0, boundBytes.Length);
            fs.Close();
        }

        s.Close();

        GetResponseDel d = new GetResponseDel(GetResponse);
        ResponseData data = new ResponseData { del = d };
        d.BeginInvoke(hr, EndGetResponse, data);

        while (!hr.HaveResponse)
        {
            Debug.Write("waiting for response" + "\n");
            Thread.Sleep(150);
        }

        Debug.Write(data.responseString);
        hr = null;
    }

    delegate WebResponse GetResponseDel(HttpWebRequest hr);
    private WebResponse GetResponse(HttpWebRequest hr)
    {
        return hr.GetResponse();
    }

    class ResponseData
    {
        public GetResponseDel del { get; set; }
        public string responseString { get; set; }
    }

    private void EndGetResponse(IAsyncResult res)
    {
        ResponseData data = (ResponseData)res.AsyncState;
        GetResponseDel d = data.del;

        WebResponse r = d.EndInvoke(res);
        data.responseString = new StreamReader(r.GetResponseStream()).ReadToEnd();
    }