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【中文标题】来自 C# 客户端的多部分表单【英文标题】：Multipart forms from C# client 【发布时间】：2010-09-18 04:52:06 【问题描述】：我正在尝试从 C# 客户端（Outlook 插件）在 php 应用程序中填写表单。我使用 Fiddler 从 php 应用程序中查看原始请求，并且表单作为 multipart/form 传输。不幸的是，.Net 并没有对这种类型的表单提供原生支持（WebClient 只有一种上传文件的方法）。 有人知道图书馆或有一些代码来实现这一点吗？我想发布不同的值和另外（但只是有时）一个文件。
感谢您的帮助， 塞巴斯蒂安
【问题讨论】：
这就像一个魅力www.briangrinstead.com/blog 如果你不介意小的库依赖，Flurl 让这变得尽可能简单。 [免责声明：我是作者] 【参考方案1】：使用 .NET 4.5，您目前可以使用 System.Net.Http 命名空间。下面是使用多部分表单数据上传单个文件的示例。
using System;
using System.IO;
using System.Net.Http;
namespace HttpClientTest
class Program
static void Main(string[] args)
var client = new HttpClient();
var content = new MultipartFormDataContent();
content.Add(new StreamContent(File.Open("../../Image1.png", FileMode.Open)), "Image", "Image.png");
content.Add(new StringContent("Place string content here"), "Content-Id in the HTTP");
var result = client.PostAsync("https://hostname/api/Account/UploadAvatar", content);
Console.WriteLine(result.Result.ToString());
【讨论】：
如果我在 URL 中获取多部分表单的详细信息，这里询问的是 pdf 等文件 您可以使用 content.Add(new StringContent("1"),"MyId"); 添加更多表单数据内容（如 Id）【参考方案2】：我的实现
/// <summary>
/// Sending file via multipart\form-data
/// </summary>
/// <param name="url">URL for send</param>
/// <param name="file">Local file path</param>
/// <param name="paramName">Request file param</param>
/// <param name="contentType">Content-Type file headr</param>
/// <param name="nvc">Additional post params</param>
private static string httpUploadFile(string url, string file, string paramName, string contentType, NameValueCollection nvc)
//delimeter
var boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
//creating request
var wr = (HttpWebRequest)WebRequest.Create(url);
wr.ContentType = "multipart/form-data; boundary=" + boundary;
wr.Method = "POST";
wr.KeepAlive = true;
//sending request
using(var requestStream = wr.GetRequestStream())
using (var requestWriter = new StreamWriter(requestStream, Encoding.UTF8))
//params
const string formdataTemplate = "Content-Disposition: form-data; name=\"0\"\r\n\r\n1";
foreach (string key in nvc.Keys)
requestWriter.Write(boundary);
requestWriter.Write(String.Format(formdataTemplate, key, nvc[key]));
requestWriter.Write(boundary);
//file header
const string headerTemplate = "Content-Disposition: form-data; name=\"0\"; filename=\"1\"\r\nContent-Type: 2\r\n\r\n";
requestWriter.Write(String.Format(headerTemplate, paramName, file, contentType));
//file content
using (var fileStream = new FileStream(file, FileMode.Open, FileAccess.Read))
fileStream.CopyTo(requestStream);
requestWriter.Write("\r\n--" + boundary + "--\r\n");
//reading response
try
using (var wresp = (HttpWebResponse)wr.GetResponse())
if (wresp.StatusCode == HttpStatusCode.OK)
using (var responseStream = wresp.GetResponseStream())
if (responseStream == null)
return null;
using (var responseReader = new StreamReader(responseStream))
return responseReader.ReadToEnd();
throw new ApplicationException("Error while upload files. Server status code: " + wresp.StatusCode.ToString());
catch (Exception ex)
throw new ApplicationException("Error while uploading file", ex);
【讨论】：
【参考方案3】：对之前的类做了一点优化。 在这个版本中，文件并没有完全加载到内存中。
安全建议：缺少边界检查，如果文件包含边界，它将崩溃。
namespace WindowsFormsApplication1
public static class FormUpload
private static string NewDataBoundary()
Random rnd = new Random();
string formDataBoundary = "";
while (formDataBoundary.Length < 15)
formDataBoundary = formDataBoundary + rnd.Next();
formDataBoundary = formDataBoundary.Substring(0, 15);
formDataBoundary = "-----------------------------" + formDataBoundary;
return formDataBoundary;
public static HttpWebResponse MultipartFormDataPost(string postUrl, IEnumerable<Cookie> cookies, Dictionary<string, string> postParameters)
string boundary = NewDataBoundary();
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(postUrl);
// Set up the request properties
request.Method = "POST";
request.ContentType = "multipart/form-data; boundary=" + boundary;
request.UserAgent = "PhasDocAgent 1.0";
request.CookieContainer = new CookieContainer();
foreach (var cookie in cookies)
request.CookieContainer.Add(cookie);
#region WRITING STREAM
using (Stream formDataStream = request.GetRequestStream())
foreach (var param in postParameters)
if (param.Value.StartsWith("file://"))
string filepath = param.Value.Substring(7);
// Add just the first part of this param, since we will write the file data directly to the Stream
string header = string.Format("--0\r\nContent-Disposition: form-data; name=\"1\"; filename=\"2\";\r\nContent-Type: 3\r\n\r\n",
boundary,
param.Key,
Path.GetFileName(filepath) ?? param.Key,
MimeTypes.GetMime(filepath));
formDataStream.Write(Encoding.UTF8.GetBytes(header), 0, header.Length);
// Write the file data directly to the Stream, rather than serializing it to a string.
byte[] buffer = new byte[2048];
FileStream fs = new FileStream(filepath, FileMode.Open);
for (int i = 0; i < fs.Length; )
int k = fs.Read(buffer, 0, buffer.Length);
if (k > 0)
formDataStream.Write(buffer, 0, k);
i = i + k;
fs.Close();
else
string postData = string.Format("--0\r\nContent-Disposition: form-data; name=\"1\"\r\n\r\n2\r\n",
boundary,
param.Key,
param.Value);
formDataStream.Write(Encoding.UTF8.GetBytes(postData), 0, postData.Length);
// Add the end of the request
byte[] footer = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");
formDataStream.Write(footer, 0, footer.Length);
request.ContentLength = formDataStream.Length;
formDataStream.Close();
#endregion
return request.GetResponse() as HttpWebResponse;
【讨论】：
【参考方案4】：谢谢大家的回答！我最近不得不让这个工作，并大量使用你的建议。但是，有几个棘手的部分没有按预期工作，主要与实际包含文件有关（这是问题的重要部分）。这里已经有很多答案，但我认为这可能对将来的某人有用（我在网上找不到很多明确的例子）。我wrote a blog post 解释了一点。
基本上，我首先尝试将文件数据作为 UTF8 编码字符串传递，但我在编码文件时遇到了问题（对于纯文本文件它工作得很好，但是在上传 Word 文档时，例如，如果我尝试使用 Request.Files[0].SaveAs() 保存传递到发布表单的文件，在 Word 中打开文件无法正常工作。我发现如果您直接使用 Stream 写入文件数据（而不是比 StringBuilder)，它按预期工作。另外，我做了一些修改，使我更容易理解。
顺便说一下，Multipart Forms Request for Comments 和 W3C Recommendation for mulitpart/form-data 是一些有用的资源，以防有人需要参考规范。
我将 WebHelpers 类更改为更小一点，并拥有更简单的接口，现在它被称为FormUpload。如果您传递FormUpload.FileParameter，您可以传递 byte[] 内容以及文件名和内容类型，如果您传递一个字符串，它会将其视为标准名称/值组合。
这是 FormUpload 类：
// Implements multipart/form-data POST in C# http://www.ietf.org/rfc/rfc2388.txt
// http://www.briangrinstead.com/blog/multipart-form-post-in-c
public static class FormUpload
private static readonly Encoding encoding = Encoding.UTF8;
public static HttpWebResponse MultipartFormDataPost(string postUrl, string userAgent, Dictionary<string, object> postParameters)
string formDataBoundary = String.Format("----------0:N", Guid.NewGuid());
string contentType = "multipart/form-data; boundary=" + formDataBoundary;
byte[] formData = GetMultipartFormData(postParameters, formDataBoundary);
return PostForm(postUrl, userAgent, contentType, formData);
private static HttpWebResponse PostForm(string postUrl, string userAgent, string contentType, byte[] formData)
HttpWebRequest request = WebRequest.Create(postUrl) as HttpWebRequest;
if (request == null)
throw new NullReferenceException("request is not a http request");
// Set up the request properties.
request.Method = "POST";
request.ContentType = contentType;
request.UserAgent = userAgent;
request.CookieContainer = new CookieContainer();
request.ContentLength = formData.Length;
// You could add authentication here as well if needed:
// request.PreAuthenticate = true;
// request.AuthenticationLevel = System.Net.Security.AuthenticationLevel.MutualAuthRequested;
// request.Headers.Add("Authorization", "Basic " + Convert.ToBase64String(System.Text.Encoding.Default.GetBytes("username" + ":" + "password")));
// Send the form data to the request.
using (Stream requestStream = request.GetRequestStream())
requestStream.Write(formData, 0, formData.Length);
requestStream.Close();
return request.GetResponse() as HttpWebResponse;
private static byte[] GetMultipartFormData(Dictionary<string, object> postParameters, string boundary)
Stream formDataStream = new System.IO.MemoryStream();
bool needsCLRF = false;
foreach (var param in postParameters)
// Thanks to feedback from commenters, add a CRLF to allow multiple parameters to be added.
// Skip it on the first parameter, add it to subsequent parameters.
if (needsCLRF)
formDataStream.Write(encoding.GetBytes("\r\n"), 0, encoding.GetByteCount("\r\n"));
needsCLRF = true;
if (param.Value is FileParameter)
FileParameter fileToUpload = (FileParameter)param.Value;
// Add just the first part of this param, since we will write the file data directly to the Stream
string header = string.Format("--0\r\nContent-Disposition: form-data; name=\"1\"; filename=\"2\";\r\nContent-Type: 3\r\n\r\n",
boundary,
param.Key,
fileToUpload.FileName ?? param.Key,
fileToUpload.ContentType ?? "application/octet-stream");
formDataStream.Write(encoding.GetBytes(header), 0, encoding.GetByteCount(header));
// Write the file data directly to the Stream, rather than serializing it to a string.
formDataStream.Write(fileToUpload.File, 0, fileToUpload.File.Length);
else
string postData = string.Format("--0\r\nContent-Disposition: form-data; name=\"1\"\r\n\r\n2",
boundary,
param.Key,
param.Value);
formDataStream.Write(encoding.GetBytes(postData), 0, encoding.GetByteCount(postData));
// Add the end of the request. Start with a newline
string footer = "\r\n--" + boundary + "--\r\n";
formDataStream.Write(encoding.GetBytes(footer), 0, encoding.GetByteCount(footer));
// Dump the Stream into a byte[]
formDataStream.Position = 0;
byte[] formData = new byte[formDataStream.Length];
formDataStream.Read(formData, 0, formData.Length);
formDataStream.Close();
return formData;
public class FileParameter
public byte[] File get; set;
public string FileName get; set;
public string ContentType get; set;
public FileParameter(byte[] file) : this(file, null)
public FileParameter(byte[] file, string filename) : this(file, filename, null)
public FileParameter(byte[] file, string filename, string contenttype)
File = file;
FileName = filename;
ContentType = contenttype;
这里是调用代码，上传一个文件和几个普通的post参数：
// Read file data
FileStream fs = new FileStream("c:\\people.doc", FileMode.Open, FileAccess.Read);
byte[] data = new byte[fs.Length];
fs.Read(data, 0, data.Length);
fs.Close();
// Generate post objects
Dictionary<string, object> postParameters = new Dictionary<string, object>();
postParameters.Add("filename", "People.doc");
postParameters.Add("fileformat", "doc");
postParameters.Add("file", new FormUpload.FileParameter(data, "People.doc", "application/msword"));
// Create request and receive response
string postURL = "http://localhost";
string userAgent = "Someone";
HttpWebResponse webResponse = FormUpload.MultipartFormDataPost(postURL, userAgent, postParameters);
// Process response
StreamReader responseReader = new StreamReader(webResponse.GetResponseStream());
string fullResponse = responseReader.ReadToEnd();
webResponse.Close();
Response.Write(fullResponse);
【讨论】：
壮观。我进行了修改以显示进度、支持 PUT 请求并使用我自己的 cookiecontainer，但这对我上路很有帮助。 优秀的基线。我做了一些小的调整以满足我们的需求，但绝对是多部分边界发布的巨大帮助。大大简化了我的工作。谢谢 #Brian 我完全按照你的代码，但它不工作:( 所以文件在发送前先读到内存中，如果是大文件怎么办【参考方案5】：下面是我正在使用的代码
//This URL not exist, it's only an example.
string url = "http://myBox.s3.amazonaws.com/";
//Instantiate new CustomWebRequest class
CustomWebRequest wr = new CustomWebRequest(url);
//Set values for parameters
wr.ParamsCollection.Add(new ParamsStruct("key", "$filename"));
wr.ParamsCollection.Add(new ParamsStruct("acl", "public-read"));
wr.ParamsCollection.Add(new ParamsStruct("success_action_redirect", "http://www.yahoo.com"));
wr.ParamsCollection.Add(new ParamsStruct("x-amz-meta-uuid", "14365123651274"));
wr.ParamsCollection.Add(new ParamsStruct("x-amz-meta-tag", ""));
wr.ParamsCollection.Add(new ParamsStruct("AWSAccessKeyId", "zzzz"));
wr.ParamsCollection.Add(new ParamsStruct("Policy", "adsfadsf"));
wr.ParamsCollection.Add(new ParamsStruct("Signature", "hH6lK6cA="));
//For file type, send the inputstream of selected file
StreamReader sr = new StreamReader(@"file.txt");
wr.ParamsCollection.Add(new ParamsStruct("file", sr, ParamsStruct.ParamType.File, "file.txt"));
wr.PostData();
我从以下链接下载了相同的代码 http://www.codeproject.com/KB/cs/multipart_request_C_.aspx
任何帮助
【讨论】：
【参考方案6】：感谢代码，它为我节省了很多时间（包括 except100 错误！）。
无论如何，我在代码中发现了一个错误，在这里：
formDataStream.Write(encoding.GetBytes(postData), 0, postData.Length);
如果您的 POST 数据是 utf-16，postData.Length 将返回字符数而不是字节数。这将截断正在发布的数据（例如，如果您有 2 个编码为 utf-16 的字符，它们占用 4 个字节，但 postData.Length 会说它占用 2 个字节，并且您丢失了已发布的 2 个最终字节数据）。
解决方案 - 将该行替换为：
byte[] aPostData=encoding.GetBytes(postData);
formDataStream.Write(aPostData, 0, aPostData.Length);
使用这个，长度是根据字节[]的大小来计算的，而不是字符串的大小。
【讨论】：
如果您只需要确定字节数，encoding.GetByteCount(postData) 可能是更好的选择【参考方案7】：在我使用的 .NET 版本中，您也必须这样做：
System.Net.ServicePointManager.Expect100Continue = false;
如果不这样做，HttpWebRequest 类将自动添加 Expect:100-continue 请求标头，这会搞砸一切。
我也学到了必须有正确数量的破折号的艰难方法。无论您说的是Content-Type 标头中的“边界”，都必须以两个破折号开头
--THEBOUNDARY
最后
--THEBOUNDARY--
与示例代码中的完全相同。如果您的边界是很多破折号后跟一个数字，那么通过查看代理服务器中的 http 请求，这个错误不会很明显
【讨论】：
这很重要！非常感谢您提及这一点，否则我永远不会考虑它，这是唯一让我感到困惑的事情！【参考方案8】：我需要模拟一个浏览器登录到一个网站来获取登录cookie，登录表单是multipart/form-data。
我从这里的其他答案中获取了一些线索，然后尝试让我自己的场景发挥作用。在它正常工作之前经历了一些令人沮丧的试验和错误，但这里是代码：
public static class WebHelpers
/// <summary>
/// Post the data as a multipart form
/// </summary>
public static HttpWebResponse MultipartFormDataPost(string postUrl, string userAgent, Dictionary<string, string> values)
string formDataBoundary = "---------------------------" + WebHelpers.RandomHexDigits(12);
string contentType = "multipart/form-data; boundary=" + formDataBoundary;
string formData = WebHelpers.MakeMultipartForm(values, formDataBoundary);
return WebHelpers.PostForm(postUrl, userAgent, contentType, formData);
/// <summary>
/// Post a form
/// </summary>
public static HttpWebResponse PostForm(string postUrl, string userAgent, string contentType, string formData)
HttpWebRequest request = WebRequest.Create(postUrl) as HttpWebRequest;
if (request == null)
throw new NullReferenceException("request is not a http request");
// Add these, as we're doing a POST
request.Method = "POST";
request.ContentType = contentType;
request.UserAgent = userAgent;
request.CookieContainer = new CookieContainer();
// We need to count how many bytes we're sending.
byte[] postBytes = Encoding.UTF8.GetBytes(formData);
request.ContentLength = postBytes.Length;
using (Stream requestStream = request.GetRequestStream())
// Push it out there
requestStream.Write(postBytes, 0, postBytes.Length);
requestStream.Close();
return request.GetResponse() as HttpWebResponse;
/// <summary>
/// Generate random hex digits
/// </summary>
public static string RandomHexDigits(int count)
Random random = new Random();
StringBuilder result = new StringBuilder();
for (int i = 0; i < count; i++)
int digit = random.Next(16);
result.AppendFormat("0:x", digit);
return result.ToString();
/// <summary>
/// Turn the key and value pairs into a multipart form
/// </summary>
private static string MakeMultipartForm(Dictionary<string, string> values, string boundary)
StringBuilder sb = new StringBuilder();
foreach (var pair in values)
sb.AppendFormat("--0\r\nContent-Disposition: form-data; name=\"1\"\r\n\r\n2\r\n", boundary, pair.Key, pair.Value);
sb.AppendFormat("--0--\r\n", boundary);
return sb.ToString();
它不处理文件数据，只处理表单，因为这就是我所需要的。我是这样打电话的：
try
using (HttpWebResponse response = WebHelpers.MultipartFormDataPost(postUrl, UserAgentString, this.loginForm))
if (response != null)
Cookie loginCookie = response.Cookies["logincookie"];
.....
【讨论】：
【参考方案9】：以 dnolans 示例为基础，这是我实际可以使用的版本（边界有一些错误，未设置编码）:-)
发送数据：
HttpWebRequest oRequest = null;
oRequest = (HttpWebRequest)HttpWebRequest.Create("http://you.url.here");
oRequest.ContentType = "multipart/form-data; boundary=" + PostData.boundary;
oRequest.Method = "POST";
PostData pData = new PostData();
Encoding encoding = Encoding.UTF8;
Stream oStream = null;
/* ... set the parameters, read files, etc. IE:
pData.Params.Add(new PostDataParam("email", "example@example.com", PostDataParamType.Field));
pData.Params.Add(new PostDataParam("fileupload", "filename.txt", "filecontents" PostDataParamType.File));
*/
byte[] buffer = encoding.GetBytes(pData.GetPostData());
oRequest.ContentLength = buffer.Length;
oStream = oRequest.GetRequestStream();
oStream.Write(buffer, 0, buffer.Length);
oStream.Close();
HttpWebResponse oResponse = (HttpWebResponse)oRequest.GetResponse();
PostData 类应如下所示：
public class PostData
// Change this if you need to, not necessary
public static string boundary = "AaB03x";
private List<PostDataParam> m_Params;
public List<PostDataParam> Params
get return m_Params;
set m_Params = value;
public PostData()
m_Params = new List<PostDataParam>();
/// <summary>
/// Returns the parameters array formatted for multi-part/form data
/// </summary>
/// <returns></returns>
public string GetPostData()
StringBuilder sb = new StringBuilder();
foreach (PostDataParam p in m_Params)
sb.AppendLine("--" + boundary);
if (p.Type == PostDataParamType.File)
sb.AppendLine(string.Format("Content-Disposition: file; name=\"0\"; filename=\"1\"", p.Name, p.FileName));
sb.AppendLine("Content-Type: application/octet-stream");
sb.AppendLine();
sb.AppendLine(p.Value);
else
sb.AppendLine(string.Format("Content-Disposition: form-data; name=\"0\"", p.Name));
sb.AppendLine();
sb.AppendLine(p.Value);
sb.AppendLine("--" + boundary + "--");
return sb.ToString();
public enum PostDataParamType
Field,
File
public class PostDataParam
public PostDataParam(string name, string value, PostDataParamType type)
Name = name;
Value = value;
Type = type;
public PostDataParam(string name, string filename, string value, PostDataParamType type)
Name = name;
Value = value;
FileName = filename;
Type = type;
public string Name;
public string FileName;
public string Value;
public PostDataParamType Type;
【讨论】：
【参考方案10】：这是从我编写的一些示例代码中剪切和粘贴的，希望它可以提供基础知识。目前只支持File数据和form-data。
public class PostData
private List<PostDataParam> m_Params;
public List<PostDataParam> Params
get return m_Params;
set m_Params = value;
public PostData()
m_Params = new List<PostDataParam>();
// Add sample param
m_Params.Add(new PostDataParam("email", "MyEmail", PostDataParamType.Field));
/// <summary>
/// Returns the parameters array formatted for multi-part/form data
/// </summary>
/// <returns></returns>
public string GetPostData()
// Get boundary, default is --AaB03x
string boundary = ConfigurationManager.AppSettings["ContentBoundary"].ToString();
StringBuilder sb = new StringBuilder();
foreach (PostDataParam p in m_Params)
sb.AppendLine(boundary);
if (p.Type == PostDataParamType.File)
sb.AppendLine(string.Format("Content-Disposition: file; name=\"0\"; filename=\"1\"", p.Name, p.FileName));
sb.AppendLine("Content-Type: text/plain");
sb.AppendLine();
sb.AppendLine(p.Value);
else
sb.AppendLine(string.Format("Content-Disposition: form-data; name=\"0\"", p.Name));
sb.AppendLine();
sb.AppendLine(p.Value);
sb.AppendLine(boundary);
return sb.ToString();
public enum PostDataParamType
Field,
File
public class PostDataParam
public PostDataParam(string name, string value, PostDataParamType type)
Name = name;
Value = value;
Type = type;
public string Name;
public string FileName;
public string Value;
public PostDataParamType Type;
要发送数据，您需要：
HttpWebRequest oRequest = null;
oRequest = (HttpWebRequest)HttpWebRequest.Create(oURL.URL);
oRequest.ContentType = "multipart/form-data";
oRequest.Method = "POST";
PostData pData = new PostData();
byte[] buffer = encoding.GetBytes(pData.GetPostData());
// Set content length of our data
oRequest.ContentLength = buffer.Length;
// Dump our buffered postdata to the stream, booyah
oStream = oRequest.GetRequestStream();
oStream.Write(buffer, 0, buffer.Length);
oStream.Close();
// get the response
oResponse = (HttpWebResponse)oRequest.GetResponse();
希望这很清楚，我已经从几个来源剪切和粘贴以使其更整洁。
【讨论】：
我不认为这行得通，边界没有在 Content-Type 中定义，并且必须在每个写入的边界的左侧添加“--”和“- -”在最后一个的右侧。不要问我这个神奇的“--”是怎么出现的，官方文档中隐含了它们：w3.org/TR/html401/interact/forms.html#h-17.13.4.2如果你不喜欢像我这样神奇的要求，你会很难像我一样完成这项工作. 这段代码绝对适用于我使用过的场景。但是我看到，虽然我定义了要在发布数据中发送的完整边界，但我没有指定将其添加到整体内容中标头作为边界分隔符。至于幻数，这是由客户端确定的，以确保它是唯一的，不会出现在任何地方的内容中，更多详细信息请参见此处：w3.org/Protocols/rfc1341/7_2_Multipart.html以上是关于来自 C# 客户端的多部分表单的主要内容，如果未能解决你的问题，请参考以下文章