This article demonstrates how you can dynamically generate ASP.NET controls in runtime using the code behind code and access the properties of the dynamically created controls.

Dynamically creating ASP.NET controlsASP.NET is a very powerful and flexible technology, allowing programmers to develop sophisticated web applications within a short period of time. It is so easy to drag and drop controls in a web form and start writing the business logic in the code behind file.Ofcourse, dragging and dropping controls from the toolbox is the easiest approach. But sometimes we may need to generate ASP.NET controls in the server side using the VB.NET or C# code. For example, consider a case where you are developing an application where you want to display a list of checkboxes to the user, depending on the number of records in a database table. In this case, you cannot drag and drop few checkbox controls, because you will not know how many checkboxes you are going to need until you retrieve the records from the database.

In this article, I will discuss how you can create ASP.NET controls at runtime using C# syntax. You can easily convert this to VB.NET syntax with little effort.Create a new ASP.NET web application using Visual Studio.NET. It will create a sample web page with the name webform1.aspx. Let us use this page for our experimentation.Drag and drop a panel control into the webform. We will dynamically generate a checkbox and add to this panel.

Double click on the webform1.aspx page. This will add a page load event handler in the code behind file. Add few lines of code in the Page_Load event handler as shown below: private void Page_Load(object sender, System.EventArgs e) { CheckBox _checkbox = new CheckBox(); _checkbox.ID = "chkDynamicCheckBox"; _checkbox.Text = "This is a dynamically generated checkbox";

Panel1.Controls.Add (_checkbox); }The above code will create a checkbox dynamically and add to the panel in the form. Using this approach, you can create any other ASP.NET control during runtime and add to the form.

// Create column 2 TableCell td2 = new TableCell(); TextBox _text = new TextBox(); _text.ID = "txt_" + i.ToString(); // Add control to the table cell td2.Controls.Add(_text); // Add cell to the row tr.Cells.Add(td1); tr.Cells.Add(td2); // Add row to the table. tblDynamic.Rows.Add(tr); }}

But what will happen to the controls created during runtime? How can we access it's properties?

The easiest way to access these dynamically created textboxes is, iterate through all controls in the form and check if it is textbox. In the above example, we have prefixed the ID with "txt_" and then appended the serial number to it for all dynamically generated controls.

Use the following recursive function to iterate through the list of all controls in the form. We are passing the form itself as parameter to the the function. The function will iterate through all children of the passed control and checks if the child control is a textbox and if the id starts with "txt_". If it matches, it sets the Text property to "You Got It!"void IterateControls(Control parent){ foreach (Control child in parent.Controls) { if (child.GetType().ToString().Equals("System.Web.UI.WebControls.TextBox") && child.ID.IndexOf("txt_") == 0) { TextBox textbox = (TextBox)child; textbox.Text = "You Got It !"; }

if (child.Controls.Count > 0) { IterateControls(child); } }}How to test it?Add the above method to your code behind file. Drag and drop a button control to the form and double click on it to create a button clicked event handler. Call the above method from the button click event handler as shown below:IterateControls(this);Now, run the application and see. When you launch the application, it will dynamically create 5 textboxes and when you click on the button, it will populate the value 'You Got It !" in all the dynamically created textboxe controls.