Best way to start building a custom-rendered control?

Question

Hi, I am needing to create a custom control.

Basically, I'm wishing to create a light weight(and better using jquery) Accordion control.

What are some good references for getting started with doing such a thing. I will be deriving it from a Panel because it's very similar(just needs a bit of JS tacked onto the end) but I want it to only be able to add controls of a certain type. I'm having trouble finding any information about custom rendered controls.

Can anyone point me to some references? Also, for the ID tag in HTML, would you use UniqueID or ClientID?

Answer 1

Any good ASP.NET book should have a chapter devoted to custom controls. If all you wanted to do was add some JS to Panel I would think you could just do this:

public class AccordianPanel : System.Web.UI.WebControls.Panel
{
    protected override void OnPreRender(EventArgs e)
    {
        base.Render(writer);
        Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "accordianscript", ScriptText);
    }
}

Or create a User Control with nothing but a Panel and the javascript in the ascx. Limiting the allowed controls is problematic at best...

As for the ID, always use ClientID to reference controls in client-side script.

Answer 2

Hello,

I would consider using the AjaxControlToolkit, and look at the documentation there (on asp.net) for how to use that to create a custom control or extender. That makes it easy to create custom controls, and you can embed JQuery in those components. The ACT provides all the plumbing; there is less work for you to use the MS ajax framework and link everything together.

I've used it and it works well, though I must admit I've recently scrapped it for my set of AJAX components within my custom framework (http://www.codeplex.com/nucleo). That was for other reasons.

Answer 3

Hello,

I missed part of your question; to validate for allowing only certain controls, you can override the AddedControl method, which is called when the control gets added. You can validate control types in this method.

Or, most controls implement a custom control collection, and I believe there is a CreateControlCollection that you can use to create a custom control. This custom control collection validates the control within the Add/AddAt method.