Hello @singh dev,
hope below solution will help you,
<asp:TextBox ID="txtBorrowerBirthDate" runat="server" SkinID="text" Width="90px"
></asp:TextBox>
<asp:ImageButton ID="imgBorrowerBirthDate" runat="server" ImageUrl="~/Images/pickdt.gif">
</asp:ImageButton>
<cc1:CalendarExtender ID="CalendarExtender2" runat="server" Format="MM/dd/yyyy" PopupButtonID="imgBorrowerBirthDate"
TargetControlID="txtBorrowerBirthDate" Enabled="True">
</cc1:CalendarExtender>