Question

I am creating a web application in Asp.net and I’m still fairly new. I’m just starting to wrap my head around the basics of the ViewState. In my application, people are searching through a database and I give them ways to narrow their search. When they have entered a valid search constraint (ex: date past 10/1/11) I dynamically add another set of controls allowing them to add another constraint. I want to save the contents of the previous constraint (a set of Controls) so that I can still have it on the webpage when they enter the next constraint.

If it makes any difference, one constraint set consists of a drop-down list of attributes, a few literal control, and one or two text fields depending on what attribute was chosen from the drop down list.

How would I go about this?

Thanks so much guys.

Answer 1

The easiest way to track viewstate for dynamic controls is to recreate the controls in OnInit and assign the same ID to the controls every time the page is posted back. If the controls are assigned the same ID each time they’re created, when the ViewState is loaded, the controls will be repopulated.

protected override void OnInit(EventArgs e)
{
    TextBox txt = new TextBox();
    txt.ID = "txt1";
    this.Controls.Add(txt);
}

EDIT

To make things easier, try using the DynamicControlsPlaceHolder. Just put the control on the page, and it will persist the controls and their values behind the scenes:

http://www.denisbauer.com/ASPNETControls/DynamicControlsPlaceholder.aspx