unable to find asp checkbox by ID

Question

I am unable to find the asp:checkbox on my asp web app using the FindControl method. I put a checkbox on my form using:

<asp:CheckBox ID="test" Text="Test checkbox" runat="server" />

In my codebehind I have the following:

Control checkbox = FindControl("test");
if (checkbox != null) Debug.Print("checkbox found");
else Debug.Print("checkbox not found");

if (test.Checked) Debug.Print("checkbox is checked");
else Debug.Print("checkbox is unchecked");

however my output (with the checkbox checked) is: checkbox not found checkbox is checked

Can somebody please tell me what I am doing wrong?

Out of curiosity, why can't you just reference your checkbox without using FindControl? — AaronS, Jul 19 '12 at 16:50
If you can use firebug and try to find the id of that checkbox — huMpty duMpty, Jul 19 '12 at 16:52
@heatStroke please can you put the actual code from your code-behind — HatSoft, Jul 19 '12 at 17:01
The reason I need FindControl is because there are actually a lot of checkboxes on my form which I would like to be able to find programatically. The checkboxes are not in a panel, table or other container. — heatStroke, Jul 19 '12 at 17:09

score 4 · Accepted Answer · answered Jul 19 '12 at 17:08

The FindControl method is not recursive and will only find your control if you call it on the immediate parent of the checkbox. So for example, if the checkbox is placed inside an UpdatePanel that's also inside the Page; you need to call FindControl on the UpdatePanel and not Page.FindControl as you are doing.

The reason your output says: checkbox not found checkbox is checked is because you are calling test.checked directly, which will always work since that's the ID you gave to your checkbox.

Again, FindControl is not recursive and I am positive that's why it's failing. You can write your own "RecursiveFindControl" method but that's almost always an overkill and inefficient as hell.

Thanks, I put all of my controls in a asp:table and my problems are solved! — heatStroke, Jul 19 '12 at 18:25

score 0 · Answer 2 · answered Jul 19 '12 at 17:09

0

You can use recursive method to find the control in following way:

private Control RecursiveFindControl(Control root, string id)
{
    if (root.ID == id) return root;
    foreach (Control c in root.Controls)
    {
        Control t = RecursiveFindControl(c, id);
        if (t != null) return t;
    }
    return null;
}

Use above recursive method to find the control:

CheckBox checkbox =  RecursiveFindControl(Page, "test") as CheckBox;
if (checkbox != null) Debug.Print("checkbox found");
else Debug.Print("checkbox not found");

if (test.Checked) Debug.Print("checkbox is checked");
else Debug.Print("checkbox is unchecked");

answered Jul 19 '12 at 17:09

Akash KC

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Precisely what I think is a bad approach and you suggested it! LOL The moment one starts using this method in a control really deep in the control tree you end up with a page slow as a turtle. I had to profile a page using this technique once, and the amount of calls to the recursive function sometimes surpassed the thousands. More than 70% of the time was spent only trying to find a control that could be found in one or 2 function calls at the most. – Icarus Jul 19 '12 at 17:16
@Icarus : I am not suggesting OP to use abvoe recursive method but just giving him a alternative to find the control through recursion.... – Akash KC Jul 19 '12 at 17:25
@LolCoder: thanks for the help, I am sure this will come in handy in the future! – heatStroke Jul 19 '12 at 18:28

unable to find asp checkbox by ID

2 Answers2