FileInfo _file_info = new FileInfo(filename);
string _uri = ...;
// Create FtpWebRequest object from the Uri provided
FtpWebRequest _request = (FtpWebRequest)FtpWebRequest.Create(new Uri(_uri));
// Provide the WebPermission Credintials
_request.Credentials = ...;
// By default KeepAlive is true, where the control connection is not closed
// after a command is executed.
_request.KeepAlive = false;
// Specify the command to be executed.
_request.Method = WebRequestMethods.Ftp.UploadFile;
// Specify the data transfer type.
_request.UseBinary = true;
// Notify the server about the size of the uploaded file
_request.ContentLength = _file_info.Length;
// The buffer size is set to 2kb
int _buff_size = 2048;
byte[] _buff = new byte[_buff_size];
int _content_size = 0;
// Opens a file stream (System.IO.FileStream) to read the file to be uploaded
FileStream _fs = _file_info.OpenRead();

// Stream to which the file to be upload is written
Stream _strm = _request.GetRequestStream();
// Read from the file stream 2kb at a time
_content_size = _fs.Read(_buff, 0, _buff_size);
// Till Stream content ends
while (_content_size != 0)
{
	// Write Content from the file stream to the FTP Upload Stream
	_strm.Write(_buff, 0, _content_size);
	_content_size = _fs.Read(_buff, 0, _buff_size);
}
// Close the file stream and the Request Stream
_strm.Close();
_fs.Close();