FindControl() from UserControl inside a for loop

Question

I'm creating a usercontrol that will have a series of LinkButtons.

I've declared all of my link buttons at the top of my class

LinkButton LB1 = new LinkButton();
LinkButton LB2 = new LinkButton();
//...
LinkButton LB9 = new LinkButton();

now I'd like to be able to create a loop to access all of those link buttons so I don't have to write them all out every time.

I tried something like this within my overridden CreateChildControls() method:

for (int i = 1; i < 10; i++)
        {
            LinkButton lb = (LinkButton)FindControl("LB" + i.ToString());
            lb.Text = i.ToString() + "-Button";
        }

I keep getting an exception saying that lb.Text... is not set to an instance of an object.

I also tried giving all of my LB1, LB2 etc valid Ids.

ie: LB1.ID = "LB1";

still not dice.

how can I do this?

Answer 1

FindControl only works once those controls have been added to Controls collection, and that only happens inside the OnInit method. So you're getting an exceptions because the LB1, LB2, etc controls haven't been added to the Controls collection and FindControl is returning null.

One way you could do it is have a List<LinkButton>, then in your Init event handler, add the controls to the list.

Another way, you could use LINQ to loop through your child controls:

var ctrls = Controls.OfType<LinkButton>();

This version would return all LinkButton controls, so I'm not sure if that's exactly what you want. Again, this would only work in the Init event or later in the page cycle.

Additionally

Depending on how your page is structure, you might be better off using a Repeater control. Something like this on your .aspx/ascx file:

<asp:Repeater ID="repeater" runat="server">
    <ItemTemplate>
        <asp:LinkButton ID="btn" runat="server" />
    </ItemTemplate>
</asp:Repeater>

Then in your code behind, you'd use data-binding to set up the array and so on.