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Why label's value is changed?

I know even if the ViewState is disabled for the TextBox, we are not losing the data because it implements the IPostBackDataHandler interface.
<asp:TextBox ID="TextBox1" runat="server" EnableViewState="False"/>
But my question is why this happens for label too? Why label is not losing it's data even if the ViewState is disabled since the label doesn't implements the IPostBackDataHandler interface?
<asp:Label ID="Label1" runat="server" EnableViewState="False" ViewStateMode="Disabled"/>
TextBox definition:
public class TextBox : WebControl, IPostBackDataHandler,
Label definition:
public class Label : WebControl, ITextControl
My code:
<form id="form1" runat="server">
<div>
<asp:Label ID="Label1" runat="server" EnableViewState="False" ViewStateMode="Disabled" Text="Before click"></asp:Label>
<asp:TextBox ID="TextBox1" runat="server" EnableViewState="False"></asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_OnClick"/>
</div>
</form>
And code behind:
protected void Button1_OnClick(object sender, EventArgs e)
{
Label1.Text = "Changed.";
}
I expected to see the "Before click" in my label after I clicked the button but I see the "Changed" text in my label after I clicked the button.

Ok I deleted my previous answer, I will try to re-state it with an example.
First, as others stated, the idea of ViewState is to hold the state between postbacks, rather than during a single page load cycle, so what you're seeing is the expected behavior.
To see the difference with an example, try adding your label with 2 buttons:
<asp:Label ID="Label1" runat="server" EnableViewState="False" Text="Before click"></asp:Label>
<asp:Button ID="btn1" Text="Click" OnClick="btn1_Click" runat="server" />
<asp:Button ID="btnReset" Text="Reset" OnClick="btnReset_Click" runat="server" />
Where btn1 sets the value to "Changed", and btnReset has an empty handler.
Now with EnableViewState set to False, if you click on btn1 the page reloads, btn1_Click is executed, and the page is rendered with the label value = "Changed", if you click btnReset the page will reload again, but since view state is disabled, the label will revert to its original text "Before click"
If you set EnableViewState to True on the lable and click btn1 then btnReset, the label value will stay as "Changed", since the state is kept during postbacks
Hope that clarifies things a bit

This is going to be long and detailed.
Let's start with this markup. Almost identical to yours, with one additional button and a label. I'll explain why we need them later.
<form id="form1" runat="server">
<div>
<asp:Label ID="Label1" runat="server" EnableViewState="False" ViewStateMode="Disabled" Text="Before click"></asp:Label>
<asp:TextBox ID="TextBox1" runat="server" EnableViewState="False"></asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_OnClick"/>
<asp:Label ID="Label2" runat="server" Text="Blah" />
<asp:Button ID="Button2" runat="server" Text="Button" OnClick="Button2_OnClick"/>
</div>
</form>
And we'll use this code behind. Again, I'll explain the purpose of the second handler later on:
protected void Button1_OnClick(object sender, EventArgs e)
{
Label1.Text = "Changed";
}
protected void Button2_OnClick(object sender, EventArgs e)
{
Label2.Text = Label1.Text;
}
Let's see what happens when we initially load the page. First ASP.NET reads all the markup, and then goes through the page life cycle with all the events. In markup parsing stage Label1 gets assigned text Before click, and it is never changed later during initial load. So later during rendering phase this is what is getting rendered into HTML and sent to browser. Thus Before click is displayed on the screen. Nice and easy.
Now we click Button1. Postback occurs, which is a term that describes a request sent to the same page by one of its controls after it was initially loaded. Again, everything starts with ASP.NET parsing the markup, and again Label1 gets assigned text Before click. But then page life cycle events happen, including control event handlers. And in the handler for Button1 the text of Label1 is changed to Changed. Now here is the important thing to note: if ViewState for the Label1 was enabled, this new value would be stored in there, and so called tracking would be enabled for property Label1.Text. But ViewState is disabled, and so the new value is not stored anywhere except Label1. Next comes the rendering page stage, and since Label1.Text still holds the value Changed this is what is rendered into HTML and sent to the browser to display. Note however that this new value is not sent inside the ViewState field. As you can see, whether ViewState is enabled or not plays no role in what is displayed after this postback.
Now we'll click Button2, which would trigger another postback. Again, ASP.NET parses the markup, again Label1 gets text Before click. Then comes ViewState loading part. If ViewState for Label1.Text was enabled, it would load changed value into this property. But ViewState is disabled, and so the value stays the same. Thus, when we reach Button2 click handler, the value of Label1.Text is still Before click, which is assigned to Label2.Text. But Label2 has ViewState enabled, and so this new value for its text is stored in ViewState and sent to the client (ViewState is implemented as a hidden field on the client side). When everything gets to the browser, we can see Label1 and Label2 both displaying Before click.
And to nail it down we'll do a third postback, now clicking Button1 again. Just as during the first postback, Label1 ends up with Changed text. But what about Label2? Well, this one has ViewState enabled, so during initial markup parsing ASP.NET assigns it the value Blah, and during ViewState loading it replaces this value with Before click. Nothing else affects this value during the page life cycle (we did not click Button2 this time), and so we end up seeing Changed and Before click in the browser.
Hopefully it makes it clear what the ViewState is for and what disabling it does. If you want to dive even deeper into how ViewState works, I would greatly recommend this article: TRULY Understanding ViewState.

I think you have wrong understanding what ViewState is.
Data in ViewState is being stored BETWEEN requests, but not DURING page lifecycle.
BTW - ViewState data is generated after PreRenderComplete event in SaveStateComplete event.
https://msdn.microsoft.com/en-us/library/ms178472.aspx
If you have ViewState switched off - just think that it will not be generated in output.
During page lifecycle all data assigned to controls(and also to page fields and properties, as the page is just a class) will be rendered as you defined in aspx. But will be lost after, unless is saved in ViewState.

ASP.Net dynamically add buttons and events to AJAX Accordion Pane

I've been searching for a while on this but cant seem to get a decent answer. I am using an Accordion and dynmically adding Panes with grids on. I would also like to add a textbox and a button when each panel is added to the accordion.
//add a comments box and a submit button to the container
Button btnComments = new Button();
btnComments.ID = CheckName + "btnComment" + i;
btnComments.CommandName = "SubmitComment";
TextBox txtComments = new TextBox();
txtComments.ID = CheckName + "txtComment" + i;
pane.ContentContainer.Controls.Add(new LiteralControl("<br />"));
pane.ContentContainer.Controls.Add(txtComments);
pane.ContentContainer.Controls.Add(new LiteralControl("<br />"));
pane.ContentContainer.Controls.Add(btnComments);
The textbox and buttons appear in the accordion as expected but the event doesn't fire. I've been reading that the event needs to be added at Page_Load but the buttons dont exist at this point.
I tried adding CommandEvent to the accordion then I could capture the sender but again this isnt firing
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Panel ID="Panel1" runat="server" />
<asp:Accordion ID="Accordion1" runat="server" AutoSize="None"
RequireOpenedPane="False" SelectedIndex="-1" FadeTransitions="false" OnItemCommand="Linked_ItemCommand">
</asp:Accordion>
<br />
<p>
<asp:Button ID="btnRunChecks" runat="server" OnClick="RunChecks" Text="Run Checks" />
<asp:CheckBox ID="chkDebug" runat="server" EnableTheming="False" Text="Run in Debug mode" />
</p>
</ContentTemplate>
</asp:UpdatePanel>
Any ideas what I'm doing wrong - any pointers much appreciated. When clicking the button it just causes a postback and refresh losing the dynamically created accordion panes.

I too have faced a similar issue and after much dismay the only solution is that there is no solution to it.
When you dynamically create controls, regardless of it being for accordion, the controls get created and are sent to the client, where they are rendered as per the client's browser.
*Upon postback, there is no means of re-rendering the controls back on the server as per what you had added in the page load event. *
This was what I learnt when trying to dynamically add textboxes to a Gridview which can grow in the number of columns: Pre-add a large number of columns with visibility as false and then unhide only the number I require.
If someone out there has a better solution, I'm all game for it!

AJAX Update Panel - Action button click on drop down selection

Evening all
I have the following scenarion. I have a range of drop down menus where a clietn can select. The code below is wrapped in an update panel but without this, the button click fires a method to retrieve the number of products. So for example, an item is selected from ddlCategory, the btnValidate is clicked and the label returns the number of products within that category.
I have the following code for an update panel - I'm just not sure how to implement if effectively.
<asp:UpdatePanel ID="UpdatePanel1" runat="Server">
<ContentTemplate>
<asp:Label ID="lblSearchResultsStatus" runat="server" Text="Number of results found: "></asp:Label>
<asp:Label ID="lblSearchResults1" runat="server" Text=""></asp:Label>
<br />
<br />
<asp:Button ID="btnValidate" runat="server" Text="Validate Search"
OnClick="btnValidate_Click" Width="120px" />
</ContentTemplate>
</asp:UpdatePanel>
How do I go about wiring the update panel so that when a drop down list item is selected, the buttong is effectively clicked?
Do I have to implement something on each of the ddlSelectedIndexChanged event or is there a property within the update panel that does?
Apologies for the noob question.

The point of the UpdatePanel is to update a portion of the page with an AsyncPostBack instead of reloading the whole page, but in order for the drop-down lists to trigger an AsyncPostBack automatically, they must be on an UpdatePanel. In order to update the labels, they must be on the same UpdatePanel with the labels.
A common pattern to implement what you want to accomplish:
Put the DDLs on the UpdatePanel, and set AutoPostBack="true" on each DDL, so they trigger AsyncPostBacks.
Add an event handler for SelectedIndexChanged on each DDL (can be the same event handler).
Move whatever you do in btnValidate_Click to another method.
Call the new method from btnValidate_Click and the SelectedIndexChanged event handler(s) so they all perform the same function.

You can call your btnValidate_Click event from codebehind at any point, i.e. Page_Load
protected void Page_Load(object sender, EventArgs e)
{
btnValidate_Click(btnValidate, new EventArgs());
}

UpdatePanel and Repeater render page unresponsive after post-back

I have a page with an UpdatePanel that contains a Repeater and a text box with the number of items in the repeater. When I change the value, the page is supposed to post back and redraw the Repeater with the updated number of items. This works in principle, but the page ends up frozen after post-backs and does not accept any input - in IE 8 only. It works perfectly fine in Firefox. For instance, the context menu does not appear when I right-click in controls, and I cannot enter text in text boxes.
When I take out the UpdatePanel, the page works fine, but of course refreshes on every post-back event. This is not necessarily related to the Repeater on the page. I think I am seeing this on other pages. What's the trick here?
<asp:UpdatePanel ID="uPanel" runat="server" UpdateMode="Conditional"
EnableViewState="true" ChildrenAsTriggers="true">
<ContentTemplate>
<asp:Panel ID="Panel1" runat="server" DefaultButton="btnSubmit">
<asp:TextBox ID="tbItems" runat="server" AutoPostback="true"
OnTextChanged="textchanged_Items"/>
<asp:Repeater id="rptItems" runat="server"
OnItemDataBound="repeaterItem_Databound">
<...>
</asp:Repeater>
protected void textchanged_Items(object sender, EventArgs e) {
try {
// this methods rebinds the repeater to a List after changing
// the number of items in the list
ReflowItemRepeater();
// This is not really necessary, since Databind() appears to
// cause an update. I tried it anyways.
uPanel.Update();
}
catch (Exception ex) {
ShowError(this, "Error displaying the item list.", ex, true);
}
}
I ended up removing the update panel.
One month later, different page, I am still and again fighting this. The situation is the same.
An update panel, a repeater (actually 2 nested repeaters), and a control in the repeater that fires a postback event. The server processes the event correctly and returns control, but the browser (IE8) never refreshes the update panel. The page is unresponsive, as if in some sort of dead-lock situation. I can unlock it by clicking on a button that fires another postback event (also in the update panel). But the text boxes in the panel are not clickable or editable when this happens.
Also, it happens only the first time. Once I have "freed up" the lock, or whatever it is, it will not happen again on this page, even when I repeat the exact same steps that led to it.
When this happens, the JIT debugger does not report anything.

I would actually set Triggers within your updatepanel.
I'm not sure you need to call .Update in your code behind as the updatepanel will be updated when the trigger occurs.
Try this:

My gut feeling is that it has something to do with the use of the OnTextChanged event. For kicks, try adding a button next to the text box, and reflow the repeater when the button is clicked instead. Does IE still freeze?

So I stripped this page down to the minimum and I found out what is doing it - the AjaxToolkit:CalendarExtender. If I take it out, everything works fine. Still, I would be curious to know if there is a workaround.
Here is a link to my test page. I will keep it up for a few days.
To see the issue, select "2" from the drop-down, then type something into the first quantity field and tab out. The cursor will blink in the next field, but it does not allow input. This happened in IE8, not in Firefox.
Edit: Actually, when I went back to the full page and removed the CalendarExtender, it was still not working. I do suspect that this issue has to do with controls posting back in the UpdatePanel, but I just can't pin it down. It seems seems to be one of these things where a combination of x things does not work, while any combination of (x-1) things does work.

Regarding the initial question, here's a working sample. I don't know if it's anyhow helpful, but just to make sure...
<%# Page Language="C#" %>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server"><title>Ajax Test</title></head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager runat="server" />
<asp:UpdatePanel runat="server" ChildrenAsTriggers="true">
<ContentTemplate>
<asp:Label runat="server" AssociatedControlID="txtTest">
Enter 'fruit' or 'vegetables':
</asp:Label>
<asp:TextBox
runat="server" ID="txtTest" AutoPostBack="true"
OnTextChanged="Handler_Test_TextChanged"
/>
<asp:Repeater runat="server" ID="rptItems">
<HeaderTemplate><ul></HeaderTemplate>
<ItemTemplate><li><%# Container.DataItem.ToString() %></li></ItemTemplate>
<FooterTemplate></ul></FooterTemplate>
</asp:Repeater>
</ContentTemplate>
</asp:UpdatePanel>
</form>
</body>
</html>
<script runat="server">
static readonly string[] Fruit = new string[]
{ "Apples", "Oranges", "Bananas", "Pears" };
static readonly string[] Veg = new string[]
{ "Potatoes", "Carrots", "Tomatoes", "Onion" };
void Handler_Test_TextChanged(object s, EventArgs e)
{
if(txtTest.Text == "fruit") rptItems.DataSource = Fruit;
else if(txtTest.Text == "vegetables") rptItems.DataSource = Veg;
else return;
rptItems.DataBind();
}
</script>

Setting focus on top of the page on click of asp.net link button

I've a asp.net datagrid which shows customer order details.
Pagination at the bottom of the grid is done using datalist and asp.net Linkbutton controls.
Here is the code:
<asp:DataList ID="DataList2" runat="server" CellPadding="1" CellSpacing="1"
OnItemCommand="DataList2_ItemCommand"
OnItemDataBound="DataList2_ItemDataBound" RepeatDirection="Horizontal">
<ItemTemplate>
<asp:LinkButton ID="lnkbtnPaging" runat="server"
CommandArgument='<%# Eval("PageIndex") %>'
CommandName="lnkbtnPaging"
Text='<%# Eval("PageText") %>' />
<asp:Label runat="server" ID="lblPageSeparator" Text=" | " name=></asp:Label>
</ItemTemplate>
</asp:DataList>
When the user clicks on any page number(ie.Link button), I need to set focus on top of the page.
How do i do this?
Thanks!

I think the default behaviour would be for the page scroll position to be set back to the top of the page. Is there anything else in your page that might be overriding this behaviour?
For example:
Is your DataList inside an UpdatePanel? In that case the current scroll position will be maintained over a (partial) post-back. You would therefore need to reset the scroll position to the top of the page yourself. One way to do this would be to implement a handler for the PageRequestManager's EndRequest client-side event which would set the scroll position - this thread explains how
Is the Page MaintainScrollPositionOnPostBack property set to true?

You could try setting a named anchor at the top of the page. Here is an article that explains it http://www.w3schools.com/HTML/html_links.asp

After an AJAX partial postback you may need to return to the top of your ASPX page to display an error message, etc. Here is one way that I have done it. You can add the JavaScript function below to your ASPX page and then call the method when needed in your code-behind by using the ScriptManager.RegisterClientScriptBlock method.
ASP.NET C# Code-behind:
ScriptManager.RegisterClientScriptBlock(this, Page.GetType(),
"ToTheTop", "ToTopOfPage();", true);
JavaScript:
<script type="text/javascript">
function ToTopOfPage(sender, args) {
setTimeout("window.scrollTo(0, 0)", 0);
}
You can also just JavaScript to scroll to the top of the page by using the OnClientClick property of your button. But this will cause this behavior to occur every time the button is clicked and not just when you want it to happen. For example:
<asp:Button id="bntTest" runat="server"
Text="Test" OnClick="btn_Test" OnClientClick="javascript:window.scrollTo(0,0);" />

<asp:LinkButton ID="lbGonder" runat="server" CssClass="IK-get" ValidationGroup="ik" OnClick="lbGonder_Click" OnClientClick="ddd();" title="Gönder">Gönder</asp:LinkButton>`
<script type="text/javascript">
var ddd = (function () {
$('body,html').animate({
scrollTop: 300
}, 1453);
return false;
});