UpdatePanel Does Not Update with Preloaded Data - asp.net

Question

I have an update panel with some textboxes and a button inside. When nothing is preloded into the textbox and I enter the data and click on the button the update panel works fine, but when data is preloaded onto the textbox onload, the update panel would not update my data and the server does not grab the data that was entered onto the textbox. Below is a sample code. Please help.
<asp:UpdatePanel runat="server" id="UpdatePanel1" UpdateMode="Conditional">
<ContentTemplate>
<asp:TextBox runat="server" Columns="30" MaxLength="50" ID="tbxPhone" onblur="PhoneBlur(this)"></asp:TextBox>
<asp:Button ID="findOrderBtn" runat="server" OnClientClick="test()" OnClick="btnSearch_Click" Text="Search..." />
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="findOrderBtn" EventName="Click" />
</Triggers>
</asp:UpdatePanel>
Below is an example of the code behind:
protected void btnSearch_Click(object sender, EventArgs e)
{
string phone = tbxPhone.Text;
}
So if tbxPhone Textbox is originally "555-555-5555" on page_load and I change it to "222-222-2222" and click on the Search... button, the data is returned is "555-555-5555" instead of "222-222-2222"

Answer 1

Here is the sample for you try this:
1.Add a script manager on your form
2.Add a update panel and do this way
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<div>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:TextBox runat="server" Text="222-222-222" ID="txtValue"></asp:TextBox>
<asp:Button ID="btnsubmit" runat="server" Text="Button" />
<asp:Label ID="lblValue" runat="server" Text="Label"></asp:Label>
</ContentTemplate>
</asp:UpdatePanel>
</div>
On button_Click event:
Protected Sub btnsubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnsubmit.Click
lblValue.Text = txtValue.Text
End Sub

Answer 2

I have an Page_Load that calls a function to pre-load data into my textbox. Once I hit the search button to update my panel, I realized that it goes through the Page_Load again hence why the data I've entered into the textbox was over written with original pre-loaded data.
Added the !IsPostBack to my Page_Load and fixed my problem.
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
// Code Here
}
}