Click here to Skip to main content
Click here to Skip to main content

Dynamically Created Controls in ASP.NET

, 27 Aug 2004 CPOL
Rate this:
Please Sign up or sign in to vote.
How to dynamically create controls in an ASP.NET page.

Introduction

Adding controls to an ASP.NET WebForm at runtime is a simple task:

private void Page_Load(object sender, System.EventArgs e)
{
    Button newButton = new Button();
    newButton.Text = "New Button"; 
    newButton.ID = "newButton"; 
    newButton.Click += new System.EventHandler(this.newButton_Click); 

    WebUserControl1 newUserControl = 
           (WebUserControl1)LoadControl("WebUserControl1.ascx"); 
    newUserControl.ID = "newUserControl";
    this.PlaceHolder.Add(newUserControl); 
    this.PlaceHolder.Add(newButton);
}

Problem

Now, let's raise a bit little. What if we want to add a new control as a result of some user action (button click, for example)? We are moving the same code from Page_Load to Button_Click event and… here troubles begin. Our controls will show as expected, but only the first time. Any postback will reset the page to its original state. Dynamically created controls will be unable to fire any event. What is happening here? The answer is simple. Page class is stateless. It is destroyed after rendering. Page recreates child controls collection, based on tags in aspx file, then postback data can be handled and event handlers attached (in OnInit event). Controls we just created dynamically do not exist in aspx file; Page has no knowledge about them.

Solution

The solution is also simple. We have to recreate controls on load stage of page lifecycle. After it's done, each control can handle its postback data, retrieve saved viewstate, raise events etc.

Now, the code skeleton will look like this:

private void Page_Load(object sender, System.EventArgs e)
{
    RecreatePersistedControls();
}
private void Button_Click(object sender, System.EventArgs e)
{
    CreateControl("newControl");
    PersistControl("newControl");
}
private void RecreatePersistedControls()
{
    // Call CreateControl for each persisted control
}
private void CreateControl(string id)
{
    // Create controll with specified id, 
    // add it to controls collection, attach event handlers
}
private void PersistControl(string id)
{
    // Persist specified id (in session for example)
}

Download source files to see the fully functional sample.

License

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

Share

About the Author

Leon Langleyben
Web Developer
Israel Israel
Leon works as Chief Architect at SRL Group. He leads architectural design and development of various enterprise level projects.
You can meet him on user groups, conferences and forums dedicated to Architecture, ASP.NET, Team System etc. or join him for the next white water rafting adventure

Comments and Discussions

 
QuestionValidating and save Dynamically created server side controls data into database Pinmemberankushbelorkar15-Feb-13 22:02 
Hello,
My form page is created with dynamic controls whose information is stored into database. when user fill all data and click submit button, i want to validate those controls and is validation successful save the user information into database. I have also applied Button click event handler but i am not able to identify which control is used for name and which for phone because i don't have control information in button click event handler. is there a way to send control information which i have retrieved from database to event handler so that i can identify controls on form depending on information which i have in database.
 
Regards.
QuestionAnother link Pinmembersandip_frm_NEPAL22-Jun-12 5:52 
Questiontotally dynamic controls Pinmembermathewtinu25-Apr-12 10:59 
Questionusing vb? PinmemberJavaCookies19-Jan-12 20:24 
AnswerRe: using vb? PinmemberMember 815202111-Dec-14 22:42 
AnswerExcellent! Pinmemberhungvm26-Mar-09 0:34 
Questionhow to add events to dynamically created and binding links PinmemberMember 40714403-Mar-09 4:32 
AnswerRe: how to add events to dynamically created and binding links Pinmemberamit_jain_online15-Apr-12 23:15 
QuestionHow do you find the path to the control later? Pinmembermicha.gluskin25-Nov-08 5:49 
GeneralAfter the Post back, control is disappeared. Pinmemberantonyvijayan3-Jun-08 2:38 
GeneralRe: After the Post back, control is disappeared. Pinmemberantonyvijayan15-Jul-08 0:25 
QuestionProb with dynamic menulist event at runtime PinmemberHarry Sun7-May-08 4:34 
QuestionImageButton help Pinmemberjdanastasi5-Apr-08 23:15 
GeneralBig Thankx Pinmemberjoeizzy24-Jun-07 17:43 
QuestionAdding controls in flow layout Pinmembermitdej10-May-07 21:56 
QuestionHow do I add radio Buttons in a table row and control them programatically Pinmembercyprosoft23-Feb-07 8:28 
Generalprob with fire eventhandeler for Dynamically Created Controls in ASP.NET Pinmemberchiluka satish16-Feb-07 13:14 
GeneralTHANK YOU THANK YOU THANK YOU THANK YOU THANK YOU Pinmemberbmatz18-Oct-06 7:38 
Questionhow to add new controls and fire its event at runtime Pinmemberdearvivek25-Sep-06 21:32 
GeneralWorks for LinkButton but not ImageButton PinmemberAndy R Hore27-Feb-06 5:39 
GeneralRe: Works for LinkButton but not ImageButton Pinmembermbsum3-Sep-06 22:09 
Generaldynamic controls and the control tree PinsussAnonymous17-Jul-05 15:37 
GeneralDynamically adding a user control based on an event from another control Pinmembersempko13-Jul-05 20:46 
GeneralRe: Dynamically adding a user control based on an event from another control PinsussAnonymous28-Aug-05 15:00 
GeneralPage Load Occurs first on Button Click Event PinsussAnonymous11-May-05 21:08 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web03 | 2.8.141223.1 | Last Updated 28 Aug 2004
Article Copyright 2004 by Leon Langleyben
Everything else Copyright © CodeProject, 1999-2014
Layout: fixed | fluid