public static string GeneratePassword(int length) {

string allowedChars = "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ0123456789!@$?";

Random rnd = new Random( (int)DateTime.Now.Ticks );
            
char[] chars = new char[length];


for(int i = 0;i<length;i++) {
chars[i] = allowedChars[ rnd.Next( allowedChars.Length ) ];
}

return new string(chars);
}

When running in a tight loop, you're better of pulling the initialisation of the randomGenerator outside the method, or not use DateTime.Now.TickCount as the seed.