Outlook.Explorer olExplorer = this.Application.ActiveExplorer();

Outlook.Folder f = olExplorer.CurrentFolder as Outlook.Folder;

Outlook.Folders olFolders = OutlookApp.Session.Folders;

for (int i = 1; i <= olFolders.Count; i++)
{
   if (olFolders[i].EntryID == olExplorer.CurrentFolder.EntryID)
   {
      // folder found assign and use it.
   }
}