Dropdownlist with the name of the month compared to the current month in C# ASP.Net

Hello there.

I have problem using this code which populates a dropdownlist with the name of the month compared to the current month. From this month on, the dropdownlist is empty. What am I doing wrong?

int currentMonth = DateTime.Today.Month;
for (int i = ddl.Items.Count; i >= 0; i--)
{
    if (i > currentMonth)
    {
        ddl.Items.RemoveAt(i - 1);
    }
}

<asp:DropDownList ID="ddl"
    runat="server"
    BackColor="Yellow"
    CssClass="pure-u-23-24">
    <asp:ListItem Text="[== ==]" Value=""></asp:ListItem>
    <asp:ListItem Text="Jan" Value="1"></asp:ListItem>
    <asp:ListItem Text="Feb" Value="2"></asp:ListItem>
    <asp:ListItem Text="Mar" Value="3"></asp:ListItem>
    <asp:ListItem Text="Apr" Value="4"></asp:ListItem>
    <asp:ListItem Text="May" Value="5"></asp:ListItem>
    <asp:ListItem Text="Jun" Value="6"></asp:ListItem>
    <asp:ListItem Text="Jul" Value="7"></asp:ListItem>
    <asp:ListItem Text="Aug" Value="8"></asp:ListItem>
    <asp:ListItem Text="Sep" Value="9"></asp:ListItem>
    <asp:ListItem Text="Oct Value="10"></asp:ListItem>
    <asp:ListItem Text="Nov" Value="11"></asp:ListItem>
    <asp:ListItem Text="Dec" Value="12"></asp:ListItem>
</asp:DropDownList>