0
Hi Sonu,
Since you are using MVC, the usual concepts we learn in ASP.NET web applications will not be applicable per se.
During MVC post, the best practice during form post is implement the PRG (Post Redirect Get) pattern to implement this kind of scenario. After posting your form, you need to redirect to your Get method so that you page will be loaded again with the required data (basically the drop down being filled again in your scenario).
Some examples of PRG pattern,
https://www.exceptionnotfound.net/the-post-redirect-get-pattern-in-asp-net-mvc/
https://www.stevefenton.co.uk/2011/04/asp-net-mvc-post-redirect-get-pattern/
http://sampathloku.blogspot.com/2013/05/how-to-use-prg-pattern-with-aspnet-mvc-4.html