How to validate textbox for date(less then today) inside a gridview using javascript

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ASP.NET

Javascript

Gridview

I need a Javascript function to validate a textbox for a date less then today's date. I have a simple date validation javascript function for textbox without a gridview. That is not helping me for validate a textbox inside a gridview.

What I have tried:

<%--<cc1:toolkitscriptmanager id="ToolkitScriptManager1" runat="server" enablepagemethods="true" enablepartialrendering="true" supportspartialrendering="true" combinescripts="false">--%>
<asp:ScriptManager ID="ScriptManager1" runat="server" EnableScriptGlobalization="true"
EnableScriptLocalization="true" />
<asp:hyperlink id="HyperLink1" style="Z-INDEX: 106; LEFT: 648px; POSITION: absolute; TOP: 112px"
runat="server" ImageUrl="home.gif" NavigateUrl="menu.aspx">HyperLink

<asp:Image ID="Image1" Style="z-index: 101; left: 0px; position: absolute; top: 0px; width: 750px;" runat="server" Height="96px" ImageUrl="images/head2.gif">

<asp:Label ID="Label1" Style="z-index: 102; left: 304px; position: absolute; top: 104px" runat="server" Font-Underline="True" ForeColor="Maroon" Font-Bold="True"> Closure of Districts

<asp:GridView ID="gvDist" runat="server" AutoGenerateColumns="False" DataKeyNames="dist_cd" Height="148px" Width="480px" Font-Size="Small" BorderWidth="1px" OnItemCommand="itemrow" CellPadding="3" BorderColor="#CCCCCC" BackColor="White" BorderStyle="None"> <columns> <asp:TemplateField HeaderText="S.no."> <itemtemplate> <asp:Label ID="lblRowNumber" Text='<%# Container.DataItemIndex + 1 %>' runat="server" /> <asp:BoundField DataField="dist_name_e" HeaderText="District" ItemStyle-Width="120px" > <itemstyle width="120px"> <asp:BoundField DataField="start_date" HeaderText="Start Date" ItemStyle-Width="120px" ApplyFormatInEditMode="true" SortExpression="SNAPSHOT_DATA_DATE" DataFormatString="{0:d}" > <itemstyle width="120px"> <asp:TemplateField HeaderText="Close Date (M-DD-YY)"> <itemtemplate> <asp:Label ID="txtDistCd" runat="server" Text='<%#Eval("dist_cd") %>' Visible="False" /> <asp:TextBox ID="txtCloseDate" runat="server" Width="80px" Text='<%#Eval("close_date", "{0:MM-dd-yyyy}")%>'> <cc1:calendarextender id="CalendarExtender2" runat="server" targetcontrolid="txtCloseDate" onclientshown="ChangeCalendarView" popupbuttonid="imgStartDate" format="dd-MM-yyyy"> <asp:ImageButton ID="imgStartDate" runat="server" ImageUrl="~/images/calender.jpg" Width="20px" /> <asp:TemplateField HeaderText="Click here"> <itemtemplate> <asp:Button ID="btnEdit" runat="server" Text="Save" CommandName="Update" /> <footerstyle forecolor="#000066" backcolor="White"> <HeaderStyle BackColor="#006699" Font-Bold="True" ForeColor="White" /> <pagerstyle backcolor="White" forecolor="#000066" horizontal=""> <rowstyle forecolor="#000066"> <SelectedRowStyle BackColor="#669999" Font-Bold="True" ForeColor="White" /> <sortedascendingcellstyle backcolor="#F1F1F1"> <sortedascendingheaderstyle backcolor="#007DBB"> <sorteddescendingcellstyle backcolor="#CAC9C9"> <sorteddescendingheaderstyle backcolor="#00547E">