Add dropdownlist and button to aspx page:
<asp:dropdownlist id="ddlTime" runat="server">
<asp:listitem text="startofday" value="1"></asp:listitem>
</asp:dropdownlist>
<asp:button id="btnAdd" runat="server" text="SignIn" onclick="DisplayAllItem" xmlns:asp="#unknown" />
Add following code in your code-behind file:
protected void DisplayAllItem(object sender, EventArgs e)
{
ddlTime.Items.Add(new ListItem("Lunchbreak", "2"));
ddlTime.Items.Add(new ListItem("teabreak", "3"));
ddlTime.Items.Add(new ListItem("dinnerbreak", "4"));
ddlTime.Items.Add(new ListItem("other", "5"));
ddlTime.Items.Add(new ListItem("endofday", "6"));
}