使用HttpWebRequest POST图片等文件，带参数

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public   static   void  HttpUploadFile( string  url,  string  file,  string  paramName,  string  contentType, NameValueCollection nvc) {
log.Debug( 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);
log.Debug( 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 ;
}
}


// 调用实例
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);


参考:
http: // stackoverflow.com/questions/566462/upload-files-with-httpwebrequest-multipart-form-data/1924810#1924810