Question

I have a custom server control inheriting from DropDownList. On postback, the items are lost. It looks something like this:

public class MyClientSelectList : DropDownList
{       
    protected override void OnInit(EventArgs e)
    {
        base.OnInit(e);

        // design mode hack to let visual studio display in design mode
        if (!DesignMode)
        {
            if (!Page.IsPostBack)
            {
                this.Items.Add(new ListItem("Select an item..."));
                // add more items from db
            }
        }
    }
}

I checked EnablePostBack = true. I select a selected value in the page load of my page which is hosting this custom server control.

Why are the items lost on postback?

Answer 1

EnableViewState is already True by default, so mshsayem’s solution will not work.
There’re 2 way to do that, a standard way is to override SaveControlState and LoadControlState Method
Refer to http://msdn.microsoft.com/en-us/library/1whwt1k7(v=VS.100).aspx

Another way is, in the Init, reload list items from database no matter postback or not, then retrieve the selected value from post data and set it back to dropdownlist