Is StreamReader.Readline() really the fastest method to count lines in a file?

Question

While looking around for a while I found quite a few discussions on how to figure out the number of lines in a file.

For example these three:
c# how do I count l

Answer 1

public static int CountLines(Stream stm)
{
    StreamReader _reader = new StreamReader(stm);
    int c = 0, count = 0;
    while ((c = _reader.Read()) != -1)
    {
        if (c == '\n')
        {
            count++;
        }
    }
    return count;
}