The Accordion in the ASP.NET AJAX Control Toolkit is a very useful tool which creates collapsible panels that open like an accordion when you click on the header. This is a good way to put content on a web page without taking up a lot of space on the page.
The problem with this control is that the first panel is always open. This doesnâ€™t matter if you have multiple panels in the control, but if you just have one panel it doesnâ€™t work well. With a single panel, it should be initially closed until you click on its header.
You can get the Accordion to default as completely closed by setting the SelectedIndex property to â€“1. The default setting is 0 which opens the first panel when the page is loaded. When you set it to â€“1, all of the panels will be closed until you click on its header. This setting makes it ideal for single panel use of this web control.