Question

I’m building an ASP.NET application. I’m using a ListView to show some Entities however my listview doesn’t have items on the first pass. I mean, they show up on the page, but this code only works when I refresh the page:

protected void Page_Load(object sender, EventArgs e)
{
    fillFeatures();
}

private void fillFeatures()
{
    using (Entities myEntities = new Entities())
    {
        System.Diagnostics.Debug.Write("Filling features.. \n");
        foreach (ListViewItem item in ListView1.Items)
        {
            System.Diagnostics.Debug.Write("FOR \n");
            CheckBox checkbox = (CheckBox)item.FindControl("Checkbox");
            TextBox description = (TextBox)item.FindControl("descriptionTextbox");

            //Try to get an existing relation
            int featureId = Int32.Parse(((Label)item.FindControl("idLabel")).Text);

            PlaceHasFeature phf = (from p in myEntities.PlaceHasFeature
                                   where p.place_id == placeId && p.feature_id == featureId
                                   select p).SingleOrDefault();

            if (phf != null)
            {
                System.Diagnostics.Debug.Write("Checking " + phf.Feature.name + "\n");
                //Relation exists
                checkbox.Checked = true;
                description.Text = phf.description;
            }
            else
            {
                System.Diagnostics.Debug.Write("Didn't find relation for " + featureId + "\n");
            }
        }
    }
}

Console output:

When I open the link: Filling features…

After refresh: Filling features… FOR FOR FOR (…)

Anyone knows the cause of this?

Answer 1

I suspect the issue is due to the ASP.NET Page Life Cycle, where the page load event occurs before the individual controls load event:

The Page object calls the OnLoad method on the Page object, and then
recursively does the same for each child control until the page and
all controls are loaded. The Load event of individual controls occurs
after the Load event of the page.

I believe you have a couple of options. Move the fillFeatures method to the Page.LoadComplete Event:

The LoadComplete event occurs after all postback data and view-state
data is loaded into the page and after the OnLoad method has been
called for all controls on the page.

Or move the fillFeatures method to the ListBox’s DataBound Event. Though I would suspect that the Page.LoadComplete Event is really the better of the two options.