How to get controls ID's on Pageload - asp.net

Question

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim lbl_Date As New Label
Dim i as int16
i = 20
While (i < i + 1)
lbl_Date = TryCast(Page.FindControl("lbl_Date" + i.ToString), Label)
lbl_Date = "Value"
i = i + 1
End While
End Sub
This is returning Nothing in lbl_Date variable. If i don't use this in Page_Load, it works just fine. Only in Page_Load it doesn't work. Any Explanation :::: Well what i am trying to do here is . i have 100 label name are lable1 to lable100. I can do like label1 =Value and label2 =Value and so on but i am trying to put in loop so i have less code. just for the Info... This code work but not in Page_Load , I am thinking every one looking to the code but this has to do with page life cycle

Answer 1

<asp:content runat="server" id="leftcontent" contentplaceholderid="LeftSidePanel" xmlns:asp="#unknown">
<div id="mydiv" runat="server">
<asp:linkbutton id="Lnk_Heading1" runat="server"> </asp:linkbutton>
<asp:label id="lbl_Date1" runat="server"> </asp:label>
<asp:label id="lbl_Detail1" runat="server"> </asp:label>
<asp:button id="Button1" runat="server" text="Button" />
</div>
</asp:content>
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim lbl_Date As New Label
Dim i as int16 i = 20
While (i < i + 1) lbl_Date = TryCast(Mydiv.FindControl("lbl_Date" + i.ToString), Label)
lbl_Date = "Value"
i = i + 1
End While
End Sub
Problem was , I didn't Used DIV in my aspx page . When i put my code in div and use the reference of the div in codebehind then it work.