c# 模拟表单提交，post form 上传文件、数据内容

转自：https://www.cnblogs.com/DoNetCShap/p/10696277.html

表单提交协议规定：
要先将 HTTP 要求的 Content-Type 设为 multipart/form-data，而且要设定一个 boundary 参数，
这个参数是由应用程序自行产生，它会用来识别每一份资料的边界 (boundary)，
用以产生多重信息部份 (message part)。
而 HTTP 服务器可以抓取 HTTP POST 的信息，

基本内容：
1. 每个信息部份都要用 --[BOUNDARY_NAME] 来包装，以分隔出信息的每个部份，而最后要再加上一个 --[BOUNDARY_NAME] 来表示结束。
2. 每个信息部份都要有一个 Content-Disposition: form-data; name=""，而 name 设定的就是 HTTP POST 的键值 (key)。
3. 声明区和值区中间要隔两个新行符号（）。
4. 中间可以夹入二进制资料，但二进制资料必须要格式化为二进制字符串。
5. 若要设定不同信息段的资料型别 (Content-Type)，则要在信息段内的声明区设定。

两个form内容模板
boundary = "----" + DateTime.Now.Ticks.ToString("x");//程序生成
1.文本内容
" --" + boundary +
" Content-Disposition: form-data; name="键"; filename="文件名"" +
" Content-Type: application/octet-stream" +
" ";
2.文件内容
" --" + boundary +
" Content-Disposition: form-data; name="键"" +
" 内容";

 1 /// <summary>
 2 /// 表单数据项
 3 /// </summary>
 4 public class FormItemModel
 5 {
 6     /// <summary>
 7     /// 表单键，request["key"]
 8     /// </summary>
 9     public string Key { set; get; }
10     /// <summary>
11     /// 表单值,上传文件时忽略，request["key"].value
12     /// </summary>
13     public string Value { set; get; }
14     /// <summary>
15     /// 是否是文件
16     /// </summary>
17     public bool IsFile
18     {
19         get
20         {
21             if (FileContent==null || FileContent.Length == 0)
22                 return false;
23  
24             if (FileContent != null && FileContent.Length > 0 && string.IsNullOrWhiteSpace(FileName))
25                 throw new Exception("上传文件时 FileName 属性值不能为空");
26             return true;
27         }
28     }
29     /// <summary>
30     /// 上传的文件名
31     /// </summary>
32     public string FileName { set; get; }
33     /// <summary>
34     /// 上传的文件内容
35     /// </summary>
36     public Stream FileContent { set; get; }
37 }

  1 /// <summary>
  2 /// 使用Post方法获取字符串结果
  3 /// </summary>
  4 /// <param name="url"></param>
  5 /// <param name="formItems">Post表单内容</param>
  6 /// <param name="cookieContainer"></param>
  7 /// <param name="timeOut">默认20秒</param>
  8 /// <param name="encoding">响应内容的编码类型（默认utf-8）</param>
  9 /// <returns></returns>
 10 public static string PostForm(string url, List<FormItemModel> formItems, CookieContainer cookieContainer = null, string refererUrl = null, Encoding encoding = null,int timeOut = 20000)
 11 {
 12     HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
 13     #region 初始化请求对象
 14     request.Method = "POST";
 15     request.Timeout = timeOut;
 16     request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";
 17     request.KeepAlive = true;
 18     request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.57 Safari/537.36";
 19     if (!string.IsNullOrEmpty(refererUrl))
 20         request.Referer = refererUrl;
 21     if (cookieContainer != null)
 22         request.CookieContainer = cookieContainer;
 23     #endregion
 24  
 25     string boundary = "----" + DateTime.Now.Ticks.ToString("x");//分隔符
 26     request.ContentType = string.Format("multipart/form-data; boundary={0}", boundary);
 27     //请求流
 28     var postStream = new MemoryStream();
 29     #region 处理Form表单请求内容
 30     //是否用Form上传文件
 31     var formUploadFile = formItems != null && formItems.Count > 0;
 32     if (formUploadFile)
 33     {
 34         //文件数据模板
 35         string fileFormdataTemplate =
 36             "
--" + boundary +
 37             "
Content-Disposition: form-data; name="{0}"; filename="{1}"" +
 38             "
Content-Type: application/octet-stream" +
 39             "

";
 40         //文本数据模板
 41         string dataFormdataTemplate =
 42             "
--" + boundary +
 43             "
Content-Disposition: form-data; name="{0}"" +
 44             "

{1}";
 45         foreach (var item in formItems)
 46         {
 47             string formdata = null;
 48             if (item.IsFile)
 49             {
 50                 //上传文件
 51                 formdata = string.Format(
 52                     fileFormdataTemplate,
 53                     item.Key, //表单键
 54                     item.FileName);
 55             }
 56             else
 57             {
 58                 //上传文本
 59                 formdata = string.Format(
 60                     dataFormdataTemplate,
 61                     item.Key,
 62                     item.Value);
 63             }
 64  
 65             //统一处理
 66             byte[] formdataBytes = null;
 67             //第一行不需要换行
 68             if (postStream.Length == 0)
 69                 formdataBytes = Encoding.UTF8.GetBytes(formdata.Substring(2, formdata.Length - 2));
 70             else
 71                 formdataBytes = Encoding.UTF8.GetBytes(formdata);
 72             postStream.Write(formdataBytes, 0, formdataBytes.Length);
 73  
 74             //写入文件内容
 75             if (item.FileContent != null && item.FileContent.Length>0)
 76             {
 77                 using (var stream = item.FileContent)
 78                 {
 79                     byte[] buffer = new byte[1024];
 80                     int bytesRead = 0;
 81                     while ((bytesRead = stream.Read(buffer, 0, buffer.Length)) != 0)
 82                     {
 83                         postStream.Write(buffer, 0, bytesRead);
 84                     }
 85                 }
 86             }
 87         }
 88         //结尾
 89         var footer = Encoding.UTF8.GetBytes("
--" + boundary + "--
");
 90         postStream.Write(footer, 0, footer.Length);
 91  
 92     }
 93     else
 94     {
 95         request.ContentType = "application/x-www-form-urlencoded";
 96     }
 97     #endregion
 98  
 99     request.ContentLength = postStream.Length;
100  
101     #region 输入二进制流
102     if (postStream != null)
103     {
104         postStream.Position = 0;
105         //直接写入流
106         Stream requestStream = request.GetRequestStream();
107  
108         byte[] buffer = new byte[1024];
109         int bytesRead = 0;
110         while ((bytesRead = postStream.Read(buffer, 0, buffer.Length)) != 0)
111         {
112             requestStream.Write(buffer, 0, bytesRead);
113         }
114  
115         ////debug
116         //postStream.Seek(0, SeekOrigin.Begin);
117         //StreamReader sr = new StreamReader(postStream);
118         //var postStr = sr.ReadToEnd();
119         postStream.Close();//关闭文件访问
120     }
121     #endregion
122  
123     HttpWebResponse response = (HttpWebResponse)request.GetResponse();
124     if (cookieContainer != null)
125     {
126         response.Cookies = cookieContainer.GetCookies(response.ResponseUri);
127     }
128  
129     using (Stream responseStream = response.GetResponseStream())
130     {
131         using (StreamReader myStreamReader = new StreamReader(responseStream, encoding ?? Encoding.UTF8))
132         {
133             string retString = myStreamReader.ReadToEnd();
134             return retString;
135         }
136     }
137 }

运行方式：

 1 var url = "http://127.0.0.1/testformdata.aspx?aa=1&bb=2&ccc=3";
 2 var log1=@"D:	emplog1.txt";
 3 var log2 = @"D:	emplog2.txt";
 4 var formDatas = new List<Grass.Net.FormItemModel>();
 5 //添加文件
 6 formDatas.Add(new Grass.Net.FormItemModel()
 7 {
 8     Key="log1",
 9     Value="",
10     FileName = "log1.txt",
11     FileContent=File.OpenRead(log1)
12 });
13 formDatas.Add(new Grass.Net.FormItemModel()
14 {
15     Key = "log2",
16     Value = "",
17     FileName = "log2.txt",
18     FileContent = File.OpenRead(log2)
19 });
20 //添加文本
21 formDatas.Add(new Grass.Net.FormItemModel()
22 {
23     Key = "id",
24     Value = "id-test-id-test-id-test-id-test-id-test-"
25 });
26 formDatas.Add(new Grass.Net.FormItemModel()
27 {
28     Key = "name",
29     Value = "name-test-name-test-name-test-name-test-name-test-"
30 });
31 //提交表单
32 var result = PostForm(url, formDatas);

以下内容做了一些优化修改：

 1 if (formUploadFile)
 2     {
 3         //文件数据模板
 4         string fileFormdataTemplate =
 5             "
--" + boundary +
 6             "
Content-Disposition: form-data; name="{0}"; filename="{1}"" +
 7             "
Content-Type: application/octet-stream" +
 8             "

";
 9         //文本数据模板
10         string dataFormdataTemplate =
11             "
--" + boundary +
12             "
Content-Disposition: form-data; name="{0}"" +
13             "

{1}";
14         //头部
15         var header = Encoding.UTF8.GetBytes("--" + boundary);
16         postStream.Write(header, 0, header.Length);
17         var index = 0;
18         foreach (var item in formItems)
19         {
20             index++;
21             string formdata = null;
22             if (item.IsFile)
23             {
24                 if (index == 1)
25                 {
26                     formdata = string.Format("
Content-Disposition: form-data; name="{0}"; filename="{1}"
Content-Type: application/octet-stream

", item.Key, item.FileName);
27  
28                 }
29                 else
30                 {
31                     //上传文件
32                     formdata = string.Format(fileFormdataTemplate,item.Key,item.FileName);
33  
34                 }
35         
36             }
37             else
38             {
39                 if (index==1)
40                 {
41                     formdata = string.Format("
Content-Disposition: form-data; name="{0}"

{1}", item.Key, item.FileName);
42                 }
43                 else
44                 {
45                     //上传文本
46                     formdata = string.Format(dataFormdataTemplate, item.Key, item.Value);
47                 }
48                  
49             }
50  
51             //统一处理
52             byte[] formdataBytes = Encoding.UTF8.GetBytes(formdata);
53  
54             postStream.Write(formdataBytes, 0, formdataBytes.Length);
55  
56             //写入文件内容
57             //if (item.FileContent != null && item.FileContent.Length > 0)
58             if (item.IsFile)
59             {
60  
61                 FileStream fs = new FileStream(item.FilePath, FileMode.Open, FileAccess.Read);//可以是其他重载方法
62                 byte[] byData = new byte[fs.Length];
63                 fs.Read(byData, 0, byData.Length);
64                 fs.Close();
65                 postStream.Write(byData, 0, byData.Length);
66             }
67         }
68         //结尾
69         var footer = Encoding.UTF8.GetBytes("
--" + boundary + "--");
70         postStream.Write(footer, 0, footer.Length);
71  
72     }