Another way to loop

alternative-looping.cs

// Alternative looping.
// I wouldn't do this using a foreach loop, but it is much nicer than
// the original here: http://stackoverflow.com/a/11367974/707111

public int getNthIndex(string str, char c, int n)
{
    int index = 0;
    int count = 0;

    if(n == 0)
        return -1;

    foreach(char i in str)
    {
        if (i == c) {
            count++;

            if (count == n)
                return index;
        }

        index++;
    }

    return -1;
}