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;
}
}