DropDownList AppendDataBoundItems (first item to be blank and no duplicates)

Question

I have a DropDownList inside an UpdatePanel that is populated on postback from a SqlDataSource. It has a parameter which is another co

Answer 1

You probably bind that DropDownList in the code behind. So you should not do it after postback again:

// probably in Page_Load method
if (!Page.IsPostBack)
{
    // do data binding here
};