R – Help with dynamically added controls in .net

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I'm stuck! I understand the page lifecycle and how i need to add the dynamic controls on page_init if I want to take advantage of viewstate. Also I know that I should try to avoid dynamic controls when possible. The dynamic controls are created depending on an object that is created from custom event arguments sent from a custom treeview. Problem is I need viewstate so I need to create them in page_init but I don't have the event args to create the object that tell me what controls to add until later in the lifecycle. Solution…

Private Function GetEventArgs() As npTreeViewEventArgs
    Dim control As Control = Nothing
    Dim e As npTreeViewEventArgs = Nothing
    Dim ctrlname As String = Page.Request.Params("__EVENTTARGET")
    Dim args As String = Request.Params("__EVENTARGUMENT")
    If ctrlname IsNot Nothing AndAlso ctrlname <> String.Empty Then
        control = Page.FindControl(ctrlname)
    End If
    If TypeOf control Is npTreeView AndAlso Not String.IsNullOrEmpty(args) Then
        e = New npTreeViewEventArgs(args)
    End If
    Return e
End Function

I use this in page_init to create my object and controls. This feels very dirty to me. Is there another way to handle this?

Best Answer

This is actually the most straightforward solution to this type of problem. If you can't add all the controls to the page on every postback and use visibility to control their appearance, then what you are doing there is exactly what I would recommend. (And have recommended before.)

I cringe when I see people resort to redirects, or implementing their own viewstate tracking, or doing extreme dynamic control manipulation to solve this. It may feel dirty, but it's infinitely more understandable and maintainable than the alternatives.

Related Solutions

C# – Problem with dynamic controls in .NET

ViewState-backed properties are only persisted to ViewState if the control is currently tracking ViewState. This is by design to keep ViewState as small as possible: it should only contain data that is truly dynamic. The upshot of this is that:

ViewState propeties set during the Init event are not backed to ViewState (because the Page has not yet started tracking ViewState). Thus Init is a good place to add controls and set (a) properties that won't change between postbacks (ID, CssClass...) as well as initial values for dynamic properties (which can then be modified by code in the rest of the page lifecycle - Load, event handlers, PreRender).

When dynamically adding controls in Load or PreRender, ViewState is being tracked. The developer can then control which propeties are persisted for dynamically added controls as follows:

Properties set before the control is added to the page's control tree are not persisted to ViewState. You typically set properties that are not dynamic (ID etc) before adding a control to the control tree.
Properties set after the control is added to the page's control tree are persisted to ViewState (ViewState tracking is enabled from before the Load Event to after the PreRender event).

In your case, your PreRender handler is setting properties before adding the control to the page's control tree. To get the result you want, set dynamic properties after adding the control to the control tree: .

protected override void OnPreRender(EventArgs e)
{
    base.OnPreRender(e);
    ValueLinkButton tempLink = new ValueLinkButton(); // [CASE 2]        
    tempLink.ID = "valueLinkButton"; // Not persisted to ViewState
    Controls.Clear();
    Controls.Add(tempLink);
    tempLink.Value = "new value";  // Persisted to ViewState
    tempLink.Text = "Click";       // Persisted to ViewState
}

C# – How to enable assembly bind failure logging (Fusion) in .NET

Add the following values to

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion
Add:
DWORD ForceLog set value to 1
DWORD LogFailures set value to 1
DWORD LogResourceBinds set value to 1
DWORD EnableLog set value to 1
String LogPath set value to folder for logs (e.g. C:\FusionLog\)

Make sure you include the backslash after the folder name and that the Folder exists.

You need to restart the program that you're running to force it to read those registry settings.

By the way, don't forget to turn off fusion logging when not needed.

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