HiddenField losing value on postback

Edkch · July 27th, 2012, 03:56 PM

Hi Imar,

I've a hidden field control on my page where its value gets lost on a postback. Is this normal? What I've is this:

In my html page, I've something like this:

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
<asp:HiddenField ID="Hidden1" runat="server" />
.
.
.
<asp:Button ID="btnCancel" Text="Cancel" runat="server" />
</asp:Content>

In my code behind, I've something like this:

protected void Page_Init(object sender, EventArgs e)
{
if (Hidden1.Value == null || Hidden1.Value == "")
{
.
.
.

Hidden1.Value = "0";
}
}

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
.
.
.

Hidden1.Value = "1";
}
}

The problem is when I click the Cancel button, which invokes the Postback, thus the Page_Init event gets called but by that time the content of Hidden1 has been reset to empty/null. And there is no code in my html page or code behind where I clear the value of Hidden1. Am I missing something, or is this the normal behavior? I wound up having to use a session variable (which I don't really like using) instead of Hidden1 for the if condition in Page_Init.

Thanks for your time and help.

Ed

Imar · July 28th, 2012, 04:27 AM

Hi Ed,

This is by design. During Init control values haven't been loaded from form and view state yet. Your code then overwrites the value and sets it to 0 again. However, if you'd debug and look at the control again in Page_Load, you'll see it still has a value of 1.

BTW: since this is not directly related to my book, you're better off posting questions like these in a more general ASP.NET category: http://p2p.wrox.com/asp-net-3-5-436/

Cheers,

Imar