Complex user input design occurs oftenly in web app. Some of requirements need multiple inputs.
Using standard textbox, radio button, check box, combo box will resulting long and a lot of form elements with so many page refresh thus this is not good enough.
Application User Easiness of use requires simple process so we need to shorten & tidy up the look & feel of UI interface.
We need more sophisticated controls to accomplish that requirement. Fortunately, Asp.Net have Ajax PopUp Extender Control.
We can create several/combined inputs inside PopUp Extender and user see it as one control. Since this control is ajax enabled then when PopUp process is happening, page will only reload partially.
Other example I want to share in this blog post is Calendar Extender Toolkit. This is basically Ajax DatePicker.
Generally, we need a textbox, PopUp panel and PopupControlExtender to form a PopUp. This textbox act as trigger also target control, PopUp panel as the popup it self and PopupControlExtender is a controller that connect popup panel with target textbox.