By default the .NET framework comes with basic Ajax controls like
UpdateProgress, etc. If you want to make the existing asp.net applications to be ajaxified then the simple and efficient way would be to make use of the extender controls which form the AJAX control toolkit. This doesn't come by default but you can download the binary from here, add it to your Microsoft Visual Studio toolbox and utilize them in you ASP.NET applications. Only thing is it requires a
ToolkitScriptManager (it is again a part of the toolkit) control on the web page which is also applicable for the basic Ajax controls.
The Ajax control kit which I am taking into consideration is targeted at ASP.NET framework 3.5 and not the 4.0.
It comes in very handy in a situation where the user has to enter a search text. It provides a way for the user to select a text displayed in the drop list or to enter a text which is altogether a new one. You shouldn't be confusing it with the dropdown list where you will not be able to type into the control.
The displayed items in the drop list should be provided through an exposed
webmethod of a web service.
Animation ExtenderIf you really want to make a jazzy web site using ASP.NET Ajax then you won't want to forget to make use of the animation control. This simplifies a lot of time spent by the developers creating animations. It can act as an extender to any ASP.NET control.
You can bring in fading, moving, resizing, coloring and many more effects easily using the animation extender. These animations can be invoked when any of the below events of the target control gets fired off.
Fig 2.0 shows a sample animation effect in a DIV tag when the target button control is clicked.
This can act as an extender control for a textbox control. On the click of the textbox the color pallet is popped out in a window which the user can make use of in order to choose a color as shown in Fig 3.0.
Without using this extender control I don't think that creating such a control would be an easy task. This is my reasoning when I included this control in this top 10 list. I should also accept the fact that requirement to use this control in a asp.net application would be very less.