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Full postback on select & remove within update panel

I'm having issues with the asp.net textbox within an update panel. It works perfectly fine when adding or removing each individual character but if I highlight all of the text within the textbox, and then remove it a full postback occurs, not a partial postback which is expected.
Why is this happening? I haven't found anything related to this particular problem so it's likely I'm doing something wrong.
Example aspx:
<asp:UpdatePanel ID="updExample" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="true">
<ContentTemplate>
<asp:Repeater ID="rptExample" runat="server" .... >
<ItemTemplate>
<asp:TextBox ID="txtExample" runat="server" ClientIDMode="static" Text='<%# Eval("Example") %>' OnTextChanged="txtExample_TextChanged" AutoPostBack="true"></asp:TextBox>
</ItemTemplate>
</asp:Repeater>
</ContentTemplate>
</asp:UpdatePanel>
Example TextChanged Event:
protected void txtExample_TextChanged(object sender, EventArgs e)
{
updExample.Update();
}
Additional Notes:
Switching UpdateMode to 'Always' doesn't work.

Karthikeyan Nagaraj pointed out in the comments to try adding triggers alongside what I already had. I did in fact already have this, however, I was assigning the trigger in the ItemDataBound event which I realized was incorrect after reinvestigating. The ItemCreated event was much more suited.
I had no issues finding the control in the ItemCreated event, however adding a new async postback trigger to the update panel gave me grief and said the control couldn't be found when changing the text. To resolve this, I used the script managers RegisterAsyncPostBackControl(); method as shown below.
protected void rptExample_ItemCreated(object sender, RepeaterItemEventArgs e)
{
var input = e.item.FindControl("txtExample");
if (input != null) {
ScriptManager sm = ScriptManager.GetCurrent(this);
sm.RegisterAsyncPostBackControl(input);
}
}

Why is my first drop down getting refreshed in a cascaded setup?

I am trying to setup a cascaded drop down box where the first one will result in the second one's value being changes and so on. I have some markup like this:
<form id="ddlSelections" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="true" />
<asp:UpdatePanel ID="UpdatePanel2" runat="server" ChildrenAsTriggers="true" UpdateMode="Conditional">
<Triggers>
<asp:AsyncPostBackTrigger ControlID="DDL1" EventName="SelectedIndexChanged" />
<asp:AsyncPostBackTrigger ControlID="DDL2" EventName="SelectedIndexChanged" />
</Triggers>
<ContentTemplate>
<asp:DropDownList ID="DDL1" OnSelectedIndexChanged="OnDDL1Change" AutoPostBack="true" runat="server" />
<asp:DropDownList ID="DDL2" OnSelectedIndexChanged="OnDDL2Change" AutoPostBack="true" runat="server" />
<asp:DropDownList ID="DDL3" runat="server" />
</ContentTemplate>
</asp:UpdatePanel>
</form>
And my code-behind is something like this:
protected void Page_Load(object sender, EventArgs e)
{
populateDDL1();
}
private void populateDDL1()
{
DDL1.Items.Clear();
// -- populate from SQL
}
protected void OnDDL1Change(object sender, EventArgs e)
{
DDL2.Items.Clear();
// -- populate from SQL
}
This is working except that everytime I click on the first drop down box, the values in the second drop down box get populated but the values in the first drop down box are being re-populated i.e. it looks like populateDDL1() is being called which of course will not be called unless Page_Load is called! I am failing to understand why this is the case. Any suggestions on where I am going wrong?

You are populating the first dropdownlist on every page load.
You need to do that only on the first load.
Wrap your populateDDL1 call in if (!IsPostBack), which is a backward way of saying to only populate it the first time the page loads.
To test this, put a breakpoint on that line in Page_Load.
Just because it's an ajax-y UpdatePanel doesn't mean that the server-side methods don't run.

Bring up input form on same page with dropdownlist?

I'm brand new at this, using vs2010 with asp.net and c#, and I'm trying to use a button click event to display forms on my "Add Product" page (the forms will be textbox/label based for inputting data), using items from a dropdownlist of products. Which methods are available/is there a 'best practice' for this sort of thing? I've been fooling around with an if (Dropdownlist.SelectedIndexChanged) statement, but I'm not quite clear on why the syntax requires the SelectedIndexChanged method to preclude a += or -=. Thoughts?

The SelectedIndexChanged method has the += because you are adding an event handler to a specific elements event. Is the button you click on the Add Product page? If so for the OnClick event you could just set your form details based on the DropDownList SelectedItem or SelectedIndex. You may also need to wrap that panel in an UpdatePanel so that it can update visibility without reloading the whole page.
<asp:UpdatePanel ID="updateFormPanel" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<asp:Label ID="lblName" runat="server" Text="" />
<asp:TextBox ID="txtDetails" runat="server" Text="" />
//More TextBox's or whatever you want
</ContentTemplate>
</asp:UpdatePanel?
<asp:DropDownList ID="ddlProductCategory" runat="server" />
<asp:Button ID="btnAddProduct" runat="server" OnClick="AddProduct_Click" Text="Add Product" />
//Code File Behind
protected void AddProduct_Click(Object sender, EventArgs e)
{
lblName.Text = ddlProductCategory.SelectedItem.Text;
txtDetails.Text = ddlProductCategory.SelectedItem.Value;
}

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());
}

ASP.NET/AJAX - Timer not working correct

I'm trying to make an webapplication where you see an Ajax countdown timer. Whenever I push a button the countdown should go back to 30 and keep counting down.
Now the problem is whenever I push the button the timer keeps counting down for a second or 2 and most of the time after that the timer keeps standing on 30 for to long.
WebForm code:
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Label ID="Label1" runat="server" Text="geen verbinding"></asp:Label>
<br />
<asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
<br />
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="Timer1" EventName="Tick" />
</Triggers>
</asp:UpdatePanel>
<asp:Timer ID="Timer1" runat="server" Interval="1000" ontick="Timer1_Tick">
</asp:Timer>
</form>
Code Behind:
static int timer = 30;
protected void Page_Load(object sender, EventArgs e)
{
Label1.Text = timer.ToString();
}
protected void Timer1_Tick(object sender, EventArgs e)
{
timer--;
}
protected void Button1_Click(object sender, EventArgs e)
{
timer = 30;
}
Hope somebody knows what the problem is and if there is anyway to fix this.
Thanks in advance!

since timer is processing the page asynchronously, and the button click event takes time for processing on the server, the timer event still fires in between the button click event and hence the timer keeps counting back for a second or two. Use Java script to set the label to 30 on client side as soon as the reset button is clicked. Upon timer click event, decrement the label value (not the timer) and assign to the label the new value. No need for timer int variable. Also on page load, assign the label value only if the page is not postback (i.e. IsPostback is false) as we want to load label value only on first time the page is rendered. Rest of the time, the timer click event will assign the value.

The problem was that Visual Studio hosted it on localhost. If you use ip-adress 127.0.0.1 instead of local host within the URL it worked fast. I guess this won't be a problem on faster machines, sadfully I had none at that time.
EDIT: Adding a bounty on this question was a mistake, sorry about that.