Finding controls in nested listviews

Question

I'm building a collapsible grouping grid using Matt Berseth's example from mattberseth.com/blog/2008/01/building_a_grouping_grid_with.html

It has an inner listview "lvInner" nested in an outer listview "lvOuter". I'm trying to access a textbox in lv_Inner using

Protected Sub lvInner_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.ListViewItemEventArgs) Handles lvInner.ItemDataBound

    If e.Item.ItemType = ListViewItemType.DataItem Then

     Dim tb As TextBox = TryCast(e.Item.FindControl("lvOuter").FindControl("lvInner").FindControl("TextBox1"), TextBox)
           ' Do something to TextBox1

     End If
EndSub

I get an "Object reference not set to an instance of an object" error on line Dim tb.

Answer 1

You need to simply do e.Item.FindControl("textbox"), e.Item is already scoped to the the proper listView.

Protected Sub lvInner_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.ListViewItemEventArgs) Handles lvInner.ItemDataBound

If e.Item.ItemType = ListViewItemType.DataItem Then

 Dim tb As TextBox = TryCast(e.Item.FindControl("TextBox1"), TextBox)
       ' Do something to TextBox1

 End If
EndSub

Answer 2

FindControl is handy, but not recursive.

If you have deep nesting of controls on a page, you might need to recursively search through the control hierarchy of the page to find the control you need.

write your own method...

C# example: (Convert using any free VBtoC# online tool)

public static System.Web.UI.Control FindControlFromTop(System.Web.UI.Control start, string id, System.Web.UI.Control exclude)
     {
      System.Web.UI.Control foundControl;

      if (start != null && id != null)
      {
       foundControl = start.FindControl(id);

       if (foundControl != null)
        if(foundControl.ID.Equals(id))
         return foundControl;

       foreach (System.Web.UI.Control control in start.Controls)
       {
        if (control != exclude)
         foundControl = FindControlFromTop(control, id, null);

        if (foundControl != null)
         if (foundControl.ID.Equals(id))
          return foundControl;
       }
      }

      return null;
     }