HTTP的POST请求的详细构造[实现机器提交表单含上传文件及普通文本域]

      最近用C#做测试网站的服务程序，由于有些接口需要真实的测试数据。比如提交表单中的文本域和文件域，但.Net中只提供了简单的单独提交文本或文件的方法，所以只能自己构造格式为

multipart/form-data

的HTTP请求，而让我更加了解了HTTP请求的格式。

      下面是在Google搜索后的一个解决方案，原链接：http://stackoverflow.com/questions/566462/upload-files-with-httpwebrequest-multipart-form-data

 方法1：上传文本域及一个文件[测试成功]

        //发送对应表单文本域和一个文件[函数中的输出语句自己调节]
        public static void HttpUploadFile(string url, string file, string paramName, string contentType, NameValueCollection nvc)
        {
            Console.WriteLine(string.Format("Uploading {0} to {1}", file, url));
            string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
            byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");

            HttpWebRequest wr = (HttpWebRequest)WebRequest.Create(url);
            wr.ContentType = "multipart/form-data; boundary=" + boundary;
            wr.Method = "POST";
            wr.KeepAlive = true;
            wr.Credentials = System.Net.CredentialCache.DefaultCredentials;

            Stream rs = wr.GetRequestStream();

            string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
            foreach (string key in nvc.Keys)
            {
                rs.Write(boundarybytes, 0, boundarybytes.Length);
                string formitem = string.Format(formdataTemplate, key, nvc[key]);
                byte[] formitembytes = System.Text.Encoding.UTF8.GetBytes(formitem);
                rs.Write(formitembytes, 0, formitembytes.Length);
            }
            rs.Write(boundarybytes, 0, boundarybytes.Length);

            string headerTemplate = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n";
            string header = string.Format(headerTemplate, paramName, file, contentType);
            byte[] headerbytes = System.Text.Encoding.UTF8.GetBytes(header);
            rs.Write(headerbytes, 0, headerbytes.Length);

            FileStream fileStream = new FileStream(file, FileMode.Open, FileAccess.Read);
            byte[] buffer = new byte[4096];
            int bytesRead = 0;
            while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
            {
                rs.Write(buffer, 0, bytesRead);
            }
            fileStream.Close();

            byte[] trailer = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
            rs.Write(trailer, 0, trailer.Length);
            rs.Close();

            WebResponse wresp = null;
            try
            {
                wresp = wr.GetResponse();
                Stream stream2 = wresp.GetResponseStream();
                StreamReader reader2 = new StreamReader(stream2);
                Console.WriteLine(string.Format("File uploaded, server response is: {0}", reader2.ReadToEnd()));
            }
            catch (Exception ex)
            {
                //log.Error("Error uploading file", ex);
                if (wresp != null)
                {
                    wresp.Close();
                    wresp = null;
                }
            }
            finally
            {
                wr = null;
            }
        }

//使用的例子
//nvc中存放表单文本域的键值对
//image/jpeg是上传文件的格式
    NameValueCollection nvc = new NameValueCollection();
    nvc.Add("id", "TTR");
    nvc.Add("btn-submit-photo", "Upload");
    HttpUploadFile("http://your.server.com/upload", 
         @"C:\test\test.jpg", "file", "image/jpeg", nvc);

方法2：上传表单文本域和多个文件[我没测试成功]

public static  void UploadFilesToRemoteUrl(string url, string[] files, string
logpath, NameValueCollection nvc)
{

    long length = 0;
    string boundary = "----------------------------" +
    DateTime.Now.Ticks.ToString("x");


    HttpWebRequest httpWebRequest2 = (HttpWebRequest)WebRequest.Create(url);
    httpWebRequest2.ContentType = "multipart/form-data; boundary=" +
    boundary;
    httpWebRequest2.Method = "POST";
    httpWebRequest2.KeepAlive = true;
    httpWebRequest2.Credentials =
    System.Net.CredentialCache.DefaultCredentials;



    Stream memStream = new System.IO.MemoryStream();

    byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" +
    boundary + "\r\n");


    string formdataTemplate = "\r\n--" + boundary +
    "\r\nContent-Disposition: form-data; name=\"{0}\";\r\n\r\n{1}";

    foreach (string key in nvc.Keys)
    {
        string formitem = string.Format(formdataTemplate, key, nvc[key]);
        byte[] formitembytes = System.Text.Encoding.UTF8.GetBytes(formitem);
        memStream.Write(formitembytes, 0, formitembytes.Length);
    }


    memStream.Write(boundarybytes, 0, boundarybytes.Length);

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

    for (int i = 0; i < files.Length; i++)
    {

        //string header = string.Format(headerTemplate, "file" + i, files[i]);
        string header = string.Format(headerTemplate, "uplTheFile", files[i]);

        byte[] headerbytes = System.Text.Encoding.UTF8.GetBytes(header);

        memStream.Write(headerbytes, 0, headerbytes.Length);


        FileStream fileStream = new FileStream(files[i], FileMode.Open,
        FileAccess.Read);
        byte[] buffer = new byte[1024];

        int bytesRead = 0;

        while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
        {
            memStream.Write(buffer, 0, bytesRead);

        }


        memStream.Write(boundarybytes, 0, boundarybytes.Length);


        fileStream.Close();
    }

    httpWebRequest2.ContentLength = memStream.Length;

    Stream requestStream = httpWebRequest2.GetRequestStream();

    memStream.Position = 0;
    byte[] tempBuffer = new byte[memStream.Length];
    memStream.Read(tempBuffer, 0, tempBuffer.Length);
    memStream.Close();
    requestStream.Write(tempBuffer, 0, tempBuffer.Length);
    requestStream.Close();


    WebResponse webResponse2 = httpWebRequest2.GetResponse();

    Stream stream2 = webResponse2.GetResponseStream();
    StreamReader reader2 = new StreamReader(stream2);


    MessageBox.Show(reader2.ReadToEnd());

    webResponse2.Close();
    httpWebRequest2 = null;
    webResponse2 = null;
}

原理解释：

详细见链接。下面简单复制过来的。

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I believe that you are not building the request body correctly. First, you need to include part boundary (random text) in content type header. For example,

Content-Type: multipart/form-data; boundary=----WebKitFormBoundarySkAQdHysJKel8YBM

Now format of request body will be something like

------WebKitFormBoundarySkAQdHysJKel8YBM 
Content-Disposition: form-data;name="key"

KeyValueGoesHere
------WebKitFormBoundarySkAQdHysJKel8YBM 
Content-Disposition: form-data;name="param2"

ValueHere
------WebKitFormBoundarySkAQdHysJKel8YBM 
Content-Disposition: form-data;name="fileUpload"; filename="y1.jpg"
Content-Type: image/jpeg 

[image data goes here]

I will suggest you to use tool such as Fiddler to understand how these requests are built.

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