Object reference not set to an instance of an object and INamingContainer
Any control that implements the INamingContainer interface creates a new control namespace which ensures that child controls have unique names on the page. If you try to directly access, for example, a TextBox within a FormView without using the FormView's FindControl() method, you will receive an "Object reference not set to an instance of an object" error. An excellent explanation of this behaviour and the FindControl() method is provided by K Scott Allen, and I won't attempt to replicate the basis of his article here. Instead, here is a list of all the standard ASP.NET web controls (System.Web.UI.Controls) that implement INamingContainer with which the FindControl method needs to be used:
- ChangePassword
- CheckBoxList
- CreateUserWizard
- DataGrid
- DataList
- DetailsView
- FormView
- GridView
- ListView
- Login
- LoginView
- LoginStatus
- Menu
- PasswordRecovery
- RadioButtonList
- SiteMapPath
There is one addition to the above list - ContentPlaceHolder - when working with MasterPages. For example, to reference a label in a FormView in a ContentPlaceHolder, you need to do something like the following:
Label lbl = this.Content1.FindControl(""FormView1").FindControl("Label1") as Label;
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Date Posted:
21 August 2007 11:36
Last Updated:
22 May 2010 19:51
Posted by:
Mikesdotnetting
Total Views to date:
17539
Comments
18 February 2009 16:06 from jkh
Error 8 'Controls' is not a member of 'DataGridTest.iX.Controls.DatePicker'. c:\inetpub\wwwroot\DataGridTest\App_Code_Old\datepicker.vb 21 32
19 February 2009 20:31 from Mikesdotnetting
@jkh
As I mentioned next to the comment form you filled in, please make sure that your comments are relevant to the topic being discussed.
I would have emailed you privately with more advice, but your obviously made-up random email address made that impossible. Bit of a waste of your time, really.
08 May 2010 07:25 from yogesh
thx so much
13 October 2010 06:07 from ramz
i cannot find the control rangevalidator in formview asp.net using findcontrol.