Information Box causing validation - asp.net

Question

I have an ASP page in which I have a file uploader. This file uploader has a required field validator attached to it. When I choose the desired file to upload the file uploads successfully and an Information Box appears with a success message.
When I click OK on the Information Box to make it go away, it attempts to validate the whole page again and the Information Box won't disappear.
I have tried setting the CausesValidation property on the file uploader to false but no luck. I've also tried AutoPostBack and IsPostBack.
aspx code
<%# Page Title="Excel File Content Upload" Language="vb" AutoEventWireup="false" MasterPageFile="~/Site.Master"
CodeBehind="ExcelFileContentUpload.aspx.vb" Inherits="Company.Applications.ProductionEngine.UI.ExcelFileContentUpload" %>
<%# Register Src="~/GenericControls/UC_InformationMessageBox.ascx" TagName="InformationBox"
TagPrefix="uc" %><asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
<h2>
<asp:Label ID="lblTitle" Text="Excel File Content Upload" runat="server" />
</h2>
<br />
<asp:FileUpload ID="fileUploader" runat="server" Width="400px"/>
<br />
<br />
Choose Year: <asp:DropDownList ID="ddlYear" runat="server"></asp:DropDownList>
Choose Month: <asp:DropDownList ID="ddlMonth" runat="server"></asp:DropDownList>
<br />
<br />
<asp:Button ID="btnDataUpload" runat="server" Text="Upload Data" CssClass="buttonBlue"
Visible="true" Width="115px"/>
<asp:UpdatePanel ID="MainContentUpdatePanel" runat="server">
<ContentTemplate>
<uc:InformationBox ID="InformationBox" runat="server" EnableViewState="true"/>
<asp:RequiredFieldValidator ID="rvfFileUploader" runat="server" ControlToValidate="fileUploader"
ErrorMessage="* Select an Excel file to upload" ForeColor="Red"></asp:RequiredFieldValidator>
</ContentTemplate>
</asp:UpdatePanel>
</asp:Content>
Page Load
#Region "PAGE LOAD"
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
'Load years and months into their respective dropdown lists
If Not Page.IsPostBack Then
Dim _currentYear As Integer = DateTime.Now.Year
Dim _previousYear As Integer = DateTime.Now.Year - 1
Dim _month = CultureInfo.CreateSpecificCulture("en").DateTimeFormat.MonthNames
For i As Integer = 0 To _month.Length - 1
ddlMonth.Items.Add(New ListItem(_month(i), i + 1).ToString())
Next
ddlYear.Items.Add(_currentYear)
ddlYear.Items.Add(_previousYear)
End If
End Sub
#End Region

Answer 1

<asp:Button ID="btnDataUpload" runat="server" Text="Upload Data" CssClass="buttonBlue" Visible="true" Width="115px" ValidationGroup="A" />
<asp:UpdatePanel ID="MainContentUpdatePanel" runat="server">
<ContentTemplate>
<uc:InformationBox ID="InformationBox" runat="server" EnableViewState="true"/>
<asp:RequiredFieldValidator ID="rvfFileUploader" runat="server" ControlToValidate="fileUploader" ErrorMessage="* Select an Excel file to upload" ForeColor="Red" ValidationGroup="A"></asp:RequiredFieldValidator>
</ContentTemplate>
</asp:UpdatePanel>
I think another option might be to take the InformationBox out of the UpdatePanel, and put the Button inside the panel, and use the defaultButton property. That works with asp:Panels easily enough.