String Lines Count

using System.Text.RegularExpressions;

public static long LineCount2(string source, bool isFileName)
{
    if (source != null)
    {
        string text = source;
        long numOfLines = 0;
        if (isFileName)
        {
            using (FileStream FS = new FileStream(source, FileMode.Open,
            FileAccess.Read, FileShare.Read))
            {
                using (StreamReader SR = new StreamReader(FS))
                {
                    while (text != null)
                    {
                        text = SR.ReadLine();
                        if (text != null)
                        {
                            ++numOfLines;
                        }
                    }
                }
            }
            return (numOfLines);
        }
        else
        {
            Regex RE = new Regex("\n", RegexOptions.Multiline);
            MatchCollection theMatches = RE.Matches(text);
            return (theMatches.Count + 1);
        }
    }
    else
    {
        // Handle a null source here.
        return (0);
    }
}