.aspx

<asp:DropDownList runat="server" ID="ddlYear"></asp:DropDownList>

 <asp:DropDownList runat="server" ID="ddlMonth"></asp:DropDownList>

.aspx.cs

private void LoadYearAndMonth()
        {
            string Year = DateTime.Now.Date.Year.ToString();
            int intYear = Convert.ToInt32(Year) + 10;
            int chaYear = intYear - 2011;
            string[] Yearlist;
            Yearlist = new string[chaYear];
            for (int i = 0; i < chaYear; i++)
            {
                Yearlist[i] = (2011 + i).ToString();
            }
            ddlYear.DataSource = Yearlist;
            ddlYear.DataBind();
            ddlYear.SelectedIndex = 0;

            string[] MonthList;
            MonthList = new string[12];
            for (int i = 0; i < 12; i++)
            {
                MonthList[i] = (i + 1).ToString("00");
            }
            ddlMonth.DataSource = MonthList;
            ddlMonth.DataBind();
            ddlMonth.SelectedIndex = 0;
        }