How to create dynamic drop down list in asp.net?

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ASP.NET

Hi,
i'm trying to develop a web page where dynamic drop down lists can be created based on few conditions.

At Database Side, a table with three columns

Column Name
===========
ID
Name
ParentID

where ID is unique sequence number, Name is the category name & ParentID is the category id to which it points to.

for example, 'a' is a category with parentid 0 & id as 1, 'b' is another category whose parentid is 1 & id as 2, and again 'c' is another category whose parentid is 2 and its id is 3, etc..

At ASP.Net Design side,

a drop down control and a textbox where drop down contains the parentid name value pairs (ID, Name). when drop down is not selected & a name is entered in the below textbox, it is created as a category with parentid as 0 (zero). whenever a drop down is selected with category name and name is entered as saved, it is saved as a sub category with parentid as category id as selected from the drop down list.

in case if the category selected in the drop down list contains further categories then here, dynamic drop down list to be display as filled with the appropriate categories as selected in the first drop down lists. in case, if the second drop down list category has further categories, then a new dynamic drop down list to be populated and filled with the appropriate categories. and this goes on & on & on ...

So, please help me in this regard.

Regards,
Rajendra Prasad