Below post explains you how to handle Cascading Dropdowns. It a good example for Ajax.
Each time the selection of one the DropDownList controls changes, the CascadingDropDown makes a call to a specified web service to retrieve the list of values for the next DropDownList in the set.
CascadingDropDown enables a common scenario in which the contents of one list depends on the selection of another list and does so without having to embed the entire data set in the page or transfer it to the client at all.
Below code explains how to handle Cascading drop downs:
Each time the selection of one the DropDownList controls changes, the CascadingDropDown makes a call to a specified web service to retrieve the list of values for the next DropDownList in the set.
CascadingDropDown enables a common scenario in which the contents of one list depends on the selection of another list and does so without having to embed the entire data set in the page or transfer it to the client at all.
Below code explains how to handle Cascading drop downs:
