using CMS.DocumentEngine;
using CMS.CMSHelper;
 
int nodeId = 241;
double rating = 1.0f;
int numOfRatings = 2;

 
// Get the document
TreeProvider tree = new TreeProvider(CMSContext.CurrentUser);
TreeNode node = tree.SelectSingleNode(nodeId, CMSContext.PreferredCultureCode);
 
// Modify its rating
TreeProvider.SetRating(node, rating, numOfRatings);