使用json 和jQuery制作级联dropdownlist

联动式的下拉选择是一个很普遍的需求，在ASP.NET MVC中可以使用Json和jQuery来实现，更简单的是使用jQuery的级联插件CascadingDropDown ，具体参见文章http://weblogs.asp.net/rajbk/archive/2010/05/20/cascadingdropdown-jquery-plugin-for-asp-net-mvc.aspx。

$(targetID).CascadingDropDown(sourceID, actionPath, settings)

•targetID
The ID of the select list that will auto populate.

•sourceID
The ID of the select list, which, on change, causes the targetID to auto populate.

•actionPath
The url to post to
Options

•promptText
Text for the first item in the select list
Default : -- Select --

•loadingText
Optional text to display in the select list while it is being loaded.
Default : Loading..

•errorText
Optional text to display if an error occurs while populating the list
Default: Error loading data.

•postData
Data you want posted to the url in place of the default
Example :
postData: function () {
    return { prefix: $('#txtPrefix').val(), customerID: $('#customerID').val() };
}
will cause prefix=foo&customerID=bar to be sent as the POST body.
Default: A text string obtained by calling serialize on the sourceID

•onLoading (event)
Raised before the list is populated.

•onLoaded (event)
Raised after the list is populated, The code below shows how to “animate” the  select list after load.