NthIndexOfCharInString

// from http://stackoverflow.com/a/6004505/1028230, edited from count to place of nth count.
public static int NthIndexOfCharInString(string strHaystack, char charNeedle, int intOccurrenceToFind)
{
    int intReturn = -1;

    int count = 0;
    int n = 0;

    while ((n = strHaystack.IndexOf(charNeedle, n)) != -1 && count < intOccurrenceToFind)
    {
        n++;
        count++;
    }

    if (count == intOccurrenceToFind) intReturn = n;

    return intReturn;
}