I am trying to change the date format in each line from commas to hyphens. The index of the comma separating the month and day day and year varies.
lines_in_List[i] = lines_in_List[i].Insert(0, cnt + ","); // Insert Draw # in 1st column
string one_line = lines_in_List[i];
// 0,5,1,2012,1,10,19,16,6,36,,,
// 1,11,5,2012,49,35,23,37,38,28,,,
// 2,12,10,2012,8,52,53,54,47,15,,,
// ^-^--^ replace the ',' with a '-'.
StringBuilder changed = new StringBuilder(one_line);
changed[3] = '-';
changed[5] = '-';
changed[3] = '-';
lines_in_List[i] = changed.ToString();
}