Hi,
You can find many samples in our
API examples.
The code for you, in this sample for document with current alias path
TreeProvider tree = new TreeProvider(CMSContext.CurrentUser);
TreeNode node = tree.SelectSingleNode(CMSContext.CurrentSiteName, CMSContext.CurrentAliasPath, "en-us");
string modDate= node.GetValue("DocumentModifiedWhen").ToString();
Best regards,
Juraj Ondrus