ASP.net .FindControl() and GridView returning null

问题

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

回答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;
        } 
    }

回答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

来源：https://stackoverflow.com/questions/13336839/asp-net-findcontrol-and-gridview-returning-null

标签

ASP.NET

gridview

findcontrol