How to save custom form control input data in web part? - kentico

Question

I followed the "Developing Custom Form Control" in kentico documentation and built a custom list box. I added the list box dynamically on the code behind and NOT adding it directly on the code front (ascx). I use the list box on one of my web parts and everything works well when I selected multiple items. However, when I click to edit the web part, all of the selected items are gone and the the list box comes back to its original form ( no item selected ). Therefore, I wonder how kentico save the old data of the form control in the web part.
On the code below, I recreate my scenario with a short version. I dynamically add the list box under a panel.
protected void EnsureItems()
{
// Create item and list box
ListBox tab = new ListBox();
ListItem item = new ListItem();
item.Text = "test";
tab.Items.Add(item);
panel.Controls.Add(tab);
}
protected void Page_Load(object sender, EventArgs e)
{
EnsureItems();
}

Answer 1

Each Form Control should be inherited from FormEngineUserControl. And Kentico utilizes Value property then to store and retrieve values from the db. Here is the example:
public override object Value
{
get
{
return listBox.SelectedValue;
}
set
{
listBox.SelectedValue = ValidationHelper.GetString(value, string.Empty);
}
}
Basically, your getter should return some value to be stored in the database. And in the setter you should initialize your listbox, fill with data and make a selection base on value coming from the database.

Answer 2

Basically, a form control itself doesn't save data to the database. The form control is attached to some form and the form saves the data to the database. Check out the documentation regarding custom form controls.