ASP.net .FindControl() and GridView returning null

Question

I have looked over the pages on the site, but cant seem to find something general enough for my problem, so was hoping someone knows what to do. I am debugging some code someone else wrote and am having problems with a GridView statement.

My problem is that my gridview is always null. I have a declared GridView in a panel which is in a LoginView, which is basically set up as the following.

<asp:LoginView ID="LoginView1" runat="server" onviewchanged="LoginView1_ViewChanged">
<AnonymousTemplate>&nbsp;Please <a href="../Default.aspx"> Log In </a></AnonymousTemplate>
<LoggedInTemplate>
        <asp:Panel ID="Panel1" runat="server">
            <asp:GridView ID="GridView1" runat="server" 
                AutoGenerateColumns="False" CellPadding="2" 
                DataSourceID="SqlDataSource1" ForeColor="Black" GridLines="Horizontal" 
                BackColor="White" BorderColor="#CCCCCC" BorderStyle="None" 
                BorderWidth="1px" Width="970px" OnRowCommand="GridView1_RowCommand" 
                PageSize="40" AllowSorting="True">

After that, in a C# file, I have the following statement

   GridView GridView1 = (GridView)LoginView1.FindControl("GridView1");

When I go to run the code, I get the NullRefrenceException on GridView1. Do I need to dig down into the panel to refrence the GridView, or should I be able to access it from the main LoginView1 segment?

Edit:Changed my code snippet to include the information for the Anonymous Template

Saiff

Are you logged in when you are doing it? What's in the anonymous template? – Sweetbread

The anonymous template is just a login screen. All the work is done through the loginview – Saiff

Answer 1

Finding the controls of a child control is an issue that comes up a lot. You can consider an extension method so you can easily call Jeff Atwood's recursive child control (as referenced in Simon's answer)... or whatever version of it you write. This is just an example using the code from that other post:

GridView GridView1 = (GridView)LoginView1.FindControlRecursive("GridView1");

Here's the code.

public static class WebControlExtender
    {
        public static Control FindControlRecursive(this Control root, string id)
        {
            if (root.ID == id)
            {
                return root;
            }

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

            return null;
        } 
    }

Sweetbread

Alright, this seems to have fixed my problem. Thank you so much – Saiff

Actually, it does not seem to work. I have implemented the code but it seems to always return null, as I still get the null exception problem. – Saiff

You never answered my other question. Are you logged in when you are doing it? What's in the anonymous template? If you aren't logged in, then yes it will be null. – Sweetbread

Sorry, I just got around to answering that. The anonymous screen is just a login screen. When I go to debug the page, the gridview is null and the page will not load for debugging, so it does not even give me the chance to log in. – Saiff

The logged in template will not be there if you aren't logged in. Paste that code into your anonymous template and you will see it work. It will help if you post your code where it is breaking. – Sweetbread

That makes it compile, is there a way to make it only work for those logged in though? As it currently is, it seems to automatically load the gridviews when you go to the page. – Saiff

Yes... don't run your code for GridView1 variable if the person isn't logged in. Or you can just check to see if it the value null. If so, don't do what you are trying to do. – Sweetbread

Ah, I got it now. Thank you for all the help Mike, kinda new to asp.net so Im not the best at it. – Saiff

Answer 2

FindControl will only check direct descendants of the control you're using it on. It won't work recursively through the childrens-children.

Jeff Atwood actually blogged about this aaaaggeesss ago:

http://www.codinghorror.com/blog/2005/06/recursive-pagefindcontrol.html

Opisthognathous