Find the line number of a string

[makdu]

hi,
i want to know the line number of a particular string in a text file.

       string filePath = @"d:\file.txt";
            StreamReader streamReader = new StreamReader(filePath);
            string text = streamReader.ReadToEnd();
           
            streamReader.Close();

            string regMatch = "Active Routes:";//string to search for inside of text file. It is case sensitive.
            if (Regex.IsMatch(text, regMatch))//If the match is found in allRead
            {
                Console.WriteLine("found\n");
                            

            }

I want to have line number of the matching string