MVC 5 application with 2 dropdowns

I want to create sample application with
2 independent dropdowns and 1 button.

It should have 1 controller, 1 view.
On calling an action, on view load, both dropdown should bind through Ajax.
Both are compulsary to select.
On button click, validation should occur using @Html.Validation....
Button click also call ajax event.
Please help me on this

I already done with the requirement, but it postback the page because, I used different way to do the functionality.