<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
		<asp:ListItem>Others</asp:ListItem>
		<asp:ListItem Selected="True">A</asp:ListItem>
		<asp:ListItem>B</asp:ListItem>
		<asp:ListItem>C</asp:ListItem>
	</asp:DropDownList>

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
	{
		Response.Write(this.DropDownList1.SelectedValue);
	}