Question

I have a dropdown list that is populated when the page loads, like this:

protected void Page_Load(object sender, EventArgs e)
{
        ddlCars.Items.Add("Ford");
        ddlCars.Items.Add("Chevy");
        ddlCars.Items.Add("BMW");
        ddlCars.Items.Add("Jeep");
        ddlCars.Items.Add("Nissan");

}

It works fine, but when a user changes the selection of the dropdown list, the list is repopulated and I see the same items twice, because the page is reloading and these values are being re-added.

What would be the best way to stop this from happening? It is important that AutoPostBack stays enabled, so that I change information based on user selection.

Thanks

Answer 1

You need to put that code in a !Page.IsPostBack block.

protected void Page_Load(object sender, EventArgs e) 
{ 
    if (!Page.IsPostBack)
    {
        ddlCars.Items.Add("Ford"); 
        ddlCars.Items.Add("Chevy"); 
        ddlCars.Items.Add("BMW"); 
        ddlCars.Items.Add("Jeep"); 
        ddlCars.Items.Add("Nissan"); 
    }
}

This will allow that code to run once (when the page loads the first time), and then be ignored whenever the page is posting back to the server due to user interaction, etc.

For more information, see Page.IsPostBack on MSDN.