Return Type: CSOM Int32
The GetUnreadMentionCount method returns the server's count of unread mentions of the current user. The server maintains a count of unread mentions in posts, but does not track which mentions have been read. When a new mention is stored on the server, it increments the unread mention for the user specified by the mention. When the unread mention count is cleared by the GetMentions method (see section 18.104.22.168.2.1.7), it is set to zero.