Using c# xmlrpc , add image into drupal 7 node

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C#

Drupal

i'm trying to add an image into a drupal 7 node. i searched the web but didn't find much. i thought of uploading an image and add it in folder(sites/all/default) but in vain. I'm getting some error in the XmlRpcClientProtocol.cs - "Could not write file to destination".
Maybe this isn't the best approach of adding and image, if you have other ideas it would be of great help.

i used file.create ethod.

XmlRpcStruct file = new XmlRpcStruct();

   file.Add("file", encodedData);
   file.Add("filename", filename);
   file.Add("filepath", "sites/default/files/" + filename);
   file.Add("filesize", filestream.Length);
   file.Add("timestamp", DateTime.Now.ToShortTimeString());

drupal.FileSave(file);

Any suggestions?