c# 模拟表单提交，post form 上传文件、大数据内容

我就是我 2024-02-17 16:37 67阅读 0赞

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（\\r\\n）。  
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  
"\\r\\n--" + boundary +  
"\\r\\nContent-Disposition: form-data; name=\\"键\\"; filename=\\"文件名\\"" +  
"\\r\\nContent-Type: application/octet-stream" +  
"\\r\\n\\r\\n";  
2.文件内容  
"\\r\\n--" + boundary +  
"\\r\\nContent-Disposition: form-data; name=\\"键\\"" +

**"\\r\\n\\r\\n内容";**

**代码  
1.表示一个表单项的对象**

/// <summary>
    /// 表单数据项
    /// </summary>
    public class FormItemModel
    {
    	/// <summary>
    	/// 表单键，request["key"]
    	/// </summary>
    	public string Key { set; get; }
    	/// <summary>
    	/// 表单值,上传文件时忽略，request["key"].value
    	/// </summary>
    	public string Value { set; get; }
    	/// <summary>
    	/// 是否是文件
    	/// </summary>
    	public bool IsFile
    	{
    		get
    		{
    			if (FileContent==null || FileContent.Length == 0)
    				return false;
    
    			if (FileContent != null && FileContent.Length > 0 && string.IsNullOrWhiteSpace(FileName))
    				throw new Exception("上传文件时 FileName 属性值不能为空");
    			return true;
    		}
    	}
    	/// <summary>
    	/// 上传的文件名
    	/// </summary>
    	public string FileName { set; get; }
    	/// <summary>
    	/// 上传的文件内容
    	/// </summary>
    	public Stream FileContent { set; get; }
    }

2.提交表单主逻辑实现

/// <summary>
    /// 使用Post方法获取字符串结果
    /// </summary>
    /// <param name="url"></param>
    /// <param name="formItems">Post表单内容</param>
    /// <param name="cookieContainer"></param>
    /// <param name="timeOut">默认20秒</param>
    /// <param name="encoding">响应内容的编码类型（默认utf-8）</param>
    /// <returns></returns>
    public static string PostForm(string url, List<FormItemModel> formItems, CookieContainer cookieContainer = null, string refererUrl = null, Encoding encoding = null,int timeOut = 20000)
    {
    	HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
    	#region 初始化请求对象
    	request.Method = "POST";
    	request.Timeout = timeOut;
    	request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";
    	request.KeepAlive = true;
    	request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.57 Safari/537.36";
    	if (!string.IsNullOrEmpty(refererUrl))
    		request.Referer = refererUrl;
    	if (cookieContainer != null)
    		request.CookieContainer = cookieContainer;
    	#endregion
    
    	string boundary = "----" + DateTime.Now.Ticks.ToString("x");//分隔符
    	request.ContentType = string.Format("multipart/form-data; boundary={0}", boundary);
    	//请求流
    	var postStream = new MemoryStream();
    	#region 处理Form表单请求内容
    	//是否用Form上传文件
    	var formUploadFile = formItems != null && formItems.Count > 0;
    	if (formUploadFile)
    	{
    		//文件数据模板
    		string fileFormdataTemplate =
    			"\r\n--" + boundary +
    			"\r\nContent-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"" +
    			"\r\nContent-Type: application/octet-stream" +
    			"\r\n\r\n";
    		//文本数据模板
    		string dataFormdataTemplate =
    			"\r\n--" + boundary +
    			"\r\nContent-Disposition: form-data; name=\"{0}\"" +
    			"\r\n\r\n{1}";
    		foreach (var item in formItems)
    		{
    			string formdata = null;
    			if (item.IsFile)
    			{
    				//上传文件
    				formdata = string.Format(
    					fileFormdataTemplate,
    					item.Key, //表单键
    					item.FileName);
    			}
    			else
    			{
    				//上传文本
    				formdata = string.Format(
    					dataFormdataTemplate,
    					item.Key,
    					item.Value);
    			}
    
    			//统一处理
    			byte[] formdataBytes = null;
    			//第一行不需要换行
    			if (postStream.Length == 0)
    				formdataBytes = Encoding.UTF8.GetBytes(formdata.Substring(2, formdata.Length - 2));
    			else
    				formdataBytes = Encoding.UTF8.GetBytes(formdata);
    			postStream.Write(formdataBytes, 0, formdataBytes.Length);
    
    			//写入文件内容
    			if (item.FileContent != null && item.FileContent.Length>0)
    			{
    				using (var stream = item.FileContent)
    				{
    					byte[] buffer = new byte[1024];
    					int bytesRead = 0;
    					while ((bytesRead = stream.Read(buffer, 0, buffer.Length)) != 0)
    					{
    						postStream.Write(buffer, 0, bytesRead);
    					}
    				}
    			}
    		}
    		//结尾
    		var footer = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");
    		postStream.Write(footer, 0, footer.Length);
    
    	}
    	else
    	{
    		request.ContentType = "application/x-www-form-urlencoded";
    	}
    	#endregion
    
    	request.ContentLength = postStream.Length;
    
    	#region 输入二进制流
    	if (postStream != null)
    	{
    		postStream.Position = 0;
    		//直接写入流
    		Stream requestStream = request.GetRequestStream();
    
    		byte[] buffer = new byte[1024];
    		int bytesRead = 0;
    		while ((bytesRead = postStream.Read(buffer, 0, buffer.Length)) != 0)
    		{
    			requestStream.Write(buffer, 0, bytesRead);
    		}
    
    		debug
    		//postStream.Seek(0, SeekOrigin.Begin);
    		//StreamReader sr = new StreamReader(postStream);
    		//var postStr = sr.ReadToEnd();
    		postStream.Close();//关闭文件访问
    	}
    	#endregion
    
    	HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    	if (cookieContainer != null)
    	{
    		response.Cookies = cookieContainer.GetCookies(response.ResponseUri);
    	}
    
    	using (Stream responseStream = response.GetResponseStream())
    	{
    		using (StreamReader myStreamReader = new StreamReader(responseStream, encoding ?? Encoding.UTF8))
    		{
    			string retString = myStreamReader.ReadToEnd();
    			return retString;
    		}
    	}
    }

3.调用模拟post表单