Setting label is always one step behind - asp.net

Question

I have the following code. I am trying to display a message when a file is to big. My problem is that the message is displayed only when I press the submit button twice. It is always one step behind. How can i fix that?
What I am doing is save a viewstate when the file is to big, and when the page loads, set the visibility of the label to true or false, depending on the file size.
I am guessing the load happens before my check, so is there another method i can use instead of Page_Load or can I do something else to make it work?
<asp:UpdatePanel ID="updatePanel" runat="server">
<ContentTemplate>
<div>
<div class="balClear">
<asp:FileUpload ID="uploader" CssClass="balUploader" runat="server"/>
<asp:ImageButton ID="uploaderEraser" CssClass="balUploaderCleaner" OnClick="uploaderEraser_Click" runat="server" Width="25" Height="25" />
</div>
<div style="clear:both">
<asp:Label ID="fileSizeError" runat="server" ForeColor="Red">The file you are trying to upload is too big. The maximul file size is 2MB.</asp:Label>
</div>
</div>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="uploaderEraser" EventName="Click" />
</Triggers>
</asp:UpdatePanel>
<asp:Button ID="submit" runat="server" Text="Submit" OnClick="submit_Click" />
cs code:
string groupURL = "~/Uploads/Group/";
string privateURL = "~/Uploads/Private/";
int maximumMB = 2;
string folderURL
{
get { return IsGroup == true ? groupURL : privateURL; }
}
public bool IsGroup
{
get { return ViewState["balUploader_IsGroup"] == null ? false : (bool)ViewState["balUploader_IsGroup"]; }
set { ViewState["balUploader_IsGroup"] = value; }
}
bool FileTooBig
{
get { return ViewState["balUploader_FileTooBig"] == null ? false : (bool)ViewState["balUploader_FileTooBig"]; }
set { ViewState["balUploader_FileTooBig"] = value; }
}
protected void Page_Load(object sender, EventArgs e)
{
if (FileTooBig == true)
{
fileSizeError.Visible = true;
}
else
{
fileSizeError.Visible = false;
}
}
public void StoreFile()
{
if (uploader.HasFile)
{
if (uploader.FileBytes.Length / 1024 / 1024 < maximumMB)
{
FileTooBig = false;
string fileName = Path.GetFileName(uploader.FileName);
uploader.SaveAs(Server.MapPath(folderURL) + fileName);
}
else
{
FileTooBig = true;
}
}
else
{
FileTooBig = false;
}
}
protected void submit_Click(object sender, EventArgs e)
{
StoreFile();
}

Answer 1

Basically, what is happening is that the submit_Click event is being fired after the Page_Load. That is due to the ASP.NET page life cycle.
The basic order of events is the following:
1 - Init
2 - Load (Page_Load is fired)
3 - Control Events (submit_Click is fired)
4 - Load Complete
5 - Pre_Render
6 - Render
You have two options here.
1 - Use the LoadComplete handler:
protected override void OnLoadComplete(EventArgs e)
{
base.OnLoadComplete(e);
//Label Logic here
}
2 - Use the OnPreRender:
protected override void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
//Label Logic here
}