private string GetAnchorPart()
{
   string anchorExp = "[#]......."; 
   Regex rex = new Regex(anchorExp); 
   Match anchorMatch = rex.Match(Request.RawUrl); 
   return anchorMatch.ToString(); 
}

Dots match any charecter, this matches any 7 chars.  You need to change that bit to match a different pattern.

Regular Expression to Separate the Anchor Part of a URL

url

C#