Controls are empty after submit

Question

I have a checkboxlist and textbox controls on my asp.net page and the are dynamically created and added to the page. When I populate the values and submit the form, the values are empty by the time it hits the server. Any help?

Answer 1

They are empty because they are being re-created too late in the page lifecycle.

Without knowing the precise point in the ASP.NET Page Lifecycle you're adding your controls, (though I'd guess it's either Page_Load or an event handler), it goes something like this:

• Build control tree
• Add dynamic controls
• Render

(Postback)

• Build control tree
• Reconstitute viewstate & bind to Post values
• Add dynamic controls
• Render

To solve this, you need to make sure your controls are created early enough in the lifecycle. Standard practice is to break the "control creation" into a separate method, and during CreateChildControls, check to see if they need to be created:

override CreateChildControls()
{
    if(IsPostBack)
    {
        EnsureDynamicControlsAreAdded();
    }
}

This way, if they do need to be initially added by something as far late in the lifecycle as an event handler (Button_Click, for example), you can call the same EnsureDynamicControlsAreAdded method from there as well, and on the next round-trip they'll be created much earlier.

Answer 2

Further to Rex M's answer, you could try creating the controls in the "Page_Init" event - this is one of the first events in the page lifecycle, and is where I would normally create controls in a viewstateless page (NB: If you do this, do not surround the content of the Page_Init handler with an "if (!IsPostback)" - this will prevent it from working as intended).