Try this
string input = "10";
int min = 0, max;
string[] items = input.Split('-');
if (items.Length == 2)
{
max = Convert.ToInt32(items[1]);
min = Convert.ToInt32(items[0]);
}
else
{
min = 1;
max = Convert.ToInt32(items[0]);
}
string output = "";
for (int i = min; i <= max; i++)
output += i + ",";
output = output.TrimEnd(',');
Console.WriteLine(output);
Console.ReadLine();