Here is a small function that might help you
private void generateSLNo(int totalRow)
{
List<string> li = new List<string>();
string s = string.Empty;
for (int i = 1; i <= 10; i++)
{
for (int j = 96; j < 123; j++)
{
if (j == 96)
{
s = s = Convert.ToString(i + ".");
}
else
{
s = Convert.ToString(i + "." + (char)j);
}
li.Add(s);
li.Add("<br>");
}
}
s = string.Empty;
for (int p = 0; p < li.Count; p++)
{
s = s + li[p].ToString();
}
lbl.Text = s;
}