how to provide textbox while uninstalling the .net application
You will need to create your own uninstaller. Such that the uninstaller uninstalls the application and provides a textbox for whatever reason that would be necessary.
Or you will need to research on how the Windows Uninstaller normally used with Control Panel to uninstall programs works so that if when installing your program there is some information that can be provided so that the Windows Uninstaller can provide a
textbox when uninstalling your program how to do that. Or if there is some method to make the Windows Uninstaller use your uninstaller instead how to do that.
Also see
Add uninstall information to Add/Remove Programs
La vida loca