How to do textchanged event with html combobox box in asp.ne

That's wonderful.

It would be really helpful, if possible, if you could please share how you managed to achieve it.

we have done....

without any script

You cannot.

That's the whole point about asp.net controls. They are managed by asp.net framework on server. On the contrary the html controls are exclusively on client side.

All you can do is probably write a javascript function on any standard event supported by html elements and post back the form there. However, asp.net on server side will not know who posted the form, so you will need to manage few things yourself.