使用multipart/form-data方式提交数据与普通的post方式有一定区别。multipart/form-data的请求头必须包含一个特殊的头信息：Content-Type，其值必须为multipart/form-data。另外还需要规定一个内容分割符用于分割请求体中的多个post的内容，如文件内容和文本内容，只有这样服务端才能正常解析数据。但是，multipart/form-data的基础还是post，它是由post方法来实现的。
点击【Code】按钮，打开如下窗体：
可以看到 Content-Type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW
以及蓝色框内的用分隔符分割的请求体中的内容。
在某些应用场景下，表单数据以键值对集合存储，然后将键值对集合上传到远程服务器。
通用方法如下：
1 /// <summary> 2 /// HTTP请求(包含表单数据) 3 /// </summary> 4 /// <param name="url">请求目标URL</param> 5 /// <param name="kvDatas">请求时表单键值对数据</param> 6 /// <param name="method">请求的方法。请使用 WebRequestMethods.Http 的枚举值</param> 7 /// <returns></returns> 8 public HttpResult UploadForm(string url, NameValueCollection kvDatas, string method = WebRequestMethods.Http.Post) 9 { 10 HttpResult httpResult = new HttpResult(); 11 HttpWebRequest httpWebRequest = null; 12 13 try 14 { 15 httpWebRequest = WebRequest.Create(url) as HttpWebRequest; 16 httpWebRequest.Method = method; 17 httpWebRequest.Headers = HeaderCollection; 18 httpWebRequest.CookieContainer = CookieContainer; 19 httpWebRequest.ContentType = HttpContentType.WWW_FORM_URLENCODED; 20 httpWebRequest.UserAgent = _userAgent; 21 httpWebRequest.AllowAutoRedirect = _allowAutoRedirect; 22 httpWebRequest.ServicePoint.Expect100Continue = false; 23 24 if (kvDatas != null) 25 { 26 StringBuilder sbKV = new StringBuilder(); 27 foreach (string key in kvDatas.Keys) 28 { 29 sbKV.AppendFormat("{0}={1}&", Uri.EscapeDataString(key), Uri.EscapeDataString(kvDatas[key])); //注意中文编码 30 } 31 32 httpWebRequest.AllowWriteStreamBuffering = true; 33 using (Stream requestStream = httpWebRequest.GetRequestStream()) 34 { 35 requestStream.Write(EncodingType.GetBytes(sbKV.ToString()), 0, sbKV.Length - 1); 36 requestStream.Flush(); 37 } 38 } 39 40 HttpWebResponse httpWebResponse = httpWebRequest.GetResponse() as HttpWebResponse; 41 if (httpWebResponse != null) 42 { 43 GetResponse(ref httpResult, httpWebResponse); 44 httpWebResponse.Close(); 45 } 46 } 47 catch (WebException webException) 48 { 49 GetWebExceptionResponse(ref httpResult, webException); 50 } 51 catch (Exception ex) 52 { 53 GetExceptionResponse(ref httpResult, ex, method, HttpContentType.WWW_FORM_URLENCODED); 54 } 55 finally 56 { 57 if (httpWebRequest != null) 58 { 59 httpWebRequest.Abort(); 60 } 61 } 62 63 return httpResult; 64 }
1、向 NameValueCollection 类中添加项时，键可以重复。
2、如果添加了C#中的某些关键字作为集合的键则会报错，解决方法是，给关键字添加前缀或者后缀，在解析时再去除前缀或者后缀。
借助于上述方法，又衍生出一个重载方法：
1 /// <summary> 2 /// HTTP请求(包含表单数据) 3 /// </summary> 4 /// <param name="url">请求目标URL</param> 5 /// <param name="kvDatas">请求时表单键值对数据</param> 6 /// <param name="method">请求的方法。请使用 WebRequestMethods.Http 的枚举值</param> 7 /// <returns></returns> 8 public HttpResult UploadForm(string url, Dictionary<string, string> kvDatas, string method = WebRequestMethods.Http.Post) 9 { 10 var nvc = kvDatas.ToNameValueCollection(); 11 12 return UploadForm(url, nvc, method); 13 }
Dictionary 字典中不能添加重复的键。
Dictionary 转换成 NameValueCollection 集合的扩展方法如下：
1 /// <summary> 2 /// 自定义扩展方法：将字典转换为 NameValueCollection 集合对象 3 /// </summary> 4 /// <param name="dict">扩展对象</param> 5 /// <returns></returns> 6 public static NameValueCollection ToNameValueCollection<TKey, TValue>(this IDictionary<TKey, TValue> dict) 7 { 8 if (dict == null) 9 { 10 return null; 11 } 12 13 var nameValueCollection = new NameValueCollection(); 14 15 foreach (var item in dict) 16 { 17 string value = null; 18 if (item.Value != null) 19 { 20 value = item.Value.ToString(); 21 } 22 23 nameValueCollection.Add(item.Key.ToString(), value); 24 } 25 26 return nameValueCollection; 27 }