how to create stop watch for on line exam in asp.net with C#

<div>        <asp:ScriptManager ID="ScriptManager1" runat="server">        </asp:ScriptManager>        <asp:UpdatePanel ID="UpdatePanel1" runat="server">            <ContentTemplate>                <asp:Timer ID="Timer1" runat="server" OnTick="Timer1_Tick">                </asp:Timer>                <br />                <br />                                <br />                <asp:Label ID="Label1" runat="server" Text="00:00"></asp:Label>                <asp:Button ID="Button1" runat="server" Text="Start" OnClick="Button1_Click" />                <asp:Button ID="Button2" runat="server" Text="Reset" OnClick="Button2_Click" />            </ContentTemplate>        </asp:UpdatePanel>    </div>