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ViewState management for dynamically loaded UserControls

, 30 Apr 2007
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ViewState management for dynamically loaded UserControls.

Introduction

In many of our business ASPX applications, there is a need for special UserControls that perform specific functionalities so that they can be easily re-used in the entire application. There are two ways we can use a UserControl: either we drag it onto the form, or we load it dynamically through the use of LoadControl("MyUserControl.ascx"). When we use the second method, we (all?) encounter one major problem: ViewState persistence! Upon postback, when we re-load the control in our CS code, .NET Framework forgets everything about its previous state. This tiny essay addresses this issue.

Solution!

Straightforward: assign the dynamically loaded control the same ID it had just before the data postback! In fact, .NET Framework retains the state of every user control (even of those dynamically loaded) and associate them with their programmatic IDs; after a postback, it tries to find the same controls with the same IDs in order to load their previous state. The whole thing can better be explained through an example Smile | :)

Example

We'll create a simple UserControl which has a TexBox, we'll also have an ASPX form on which we use this control but in three ways. For this purpose, we'll create three instances:

  • An instance which is already dragged onto the form
  • An instance dynamically created through LoadControl()
  • An instance dynamically created through LoadControl() with its ID preserved

I have created a simple UserControlViewStateManager that will help us automatically save/load the dynamically loaded controls and their IDs. The main idea behind this gadget is to save the ID of the UserControls right after loading them into their parent container and re-creating them after the postback: the best place for re-creating the controls is the Page_Init event.

When creating a new user control: just give a unique ID and at the same time, add it to an instance of the UserControlViewStateManager. Shown below is a snippet:

Control userControl = LoadControl("MyUserControl.ascx");
userControl.ID = (placeHolder2.Controls.Count - 1).ToString();
placeHolder2.Controls.Add(userControl);
ucViewStateManager.AddControl(userControl);

In the Page_Init event, call ReCreateControlsID() of the helper class, passing it the container object as a parameter:

ucViewStateManager = new UserControlViewStateManager("SomeUniqueSessionID");
ucViewStateManager.ReCreateControlsID(placeHolder2);

Hope this helps Smile | :) In the demo application, you can find the entire source code.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Wesam Elsawirki
Software Developer (Senior)
Hungary Hungary
Professional Software Developer, currently working for HVB bank.
Programming experience includes: C#, ASP.NET, Delphi, PHP, VB.
Technologies: MS SQL Server 2005, Apache, IIS.
 
Certifications: MCAD, MCSD, MCTS (MS SQL Server 2005), MCITP

Comments and Discussions

 
GeneralMessage Automatically Removed PinmemberAytha24-Nov-11 1:10 
GeneralMore about Dinamically added controls Pinmemberrafael.aca14-Apr-09 12:06 
GeneralDynamice Usercontrol .ascx PinmemberKurmala13-Jul-08 19:50 
GeneralUser Controls Piling UP on Page [modified] Pinmemberstanz927-Feb-08 7:04 
GeneralIs this a sure tested method of loading usercontrols dynamically Pinmemberxsoftdev19-Feb-08 13:12 
GeneralPass values to other user controls Pinmemberxsoftdev18-Oct-07 15:55 
GeneralRe: Pass values to other user controls PinmemberWesam E.20-Oct-07 3:56 
GeneralRe: Pass values to other user controls Pinmemberxsoftdev26-Nov-07 6:52 
GeneralLoad one and Unload the others Pinmemberxsoftdev4-Oct-07 9:00 
GeneralRe: Load one and Unload the others PinmemberWesam E.8-Oct-07 20:04 
GeneralUserControl PinmemberBrother Louis20-Aug-07 0:54 
GeneralRe: UserControl PinmemberWesam E.8-Oct-07 19:59 
Questionquestion from manish.2004 PinadminSean Ewington1-Jun-07 9:04 
AnswerRe: question from manish.2004 PinmemberWesam E.4-Oct-07 20:23 
GeneralRe: question from manish.2004 Pinmemberxsoftdev22-Nov-07 0:50 
Hello,
When are you planning to add the new version?
Thanks
QuestionIssues at Page PostBack Pinmembermkhiami27-Apr-07 10:40 
QuestionThread-Safe ??? PinmemberMarco M.18-Apr-07 9:06 
AnswerRe: Thread-Safe ??? PinmemberJohnno7423-Apr-07 16:57 
GeneralRe: Thread-Safe ??? PinmemberWesam E.30-Apr-07 0:08 
GeneralRe: Thread-Safe ??? PinmemberJohnno7430-Apr-07 12:50 
GeneralControl issue PinmemberVolleyknaller17-Apr-07 22:39 
GeneralRe: Control issue PinmemberWesam E.18-Apr-07 0:35 
GeneralRe: Control issue PinmemberVolleyknaller18-Apr-07 1:18 
QuestionPostback issue Pinmemberinetfly12317-Apr-07 11:01 
AnswerRe: Postback issue PinmemberWesam E.17-Apr-07 19:59 

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