View doesn't refresh after RedirectToAction is done

Because you are using Ajax Post

public ActionResult AddData(CandidateViewModel viewModel)  
{
    var newCandidateId = 0;  
    newCandidateId = this._serviceClient.AddCandidate(viewModel); 
    string ReturnURL = "/DisplayCandidate/"+newCandidateId;
    return JSON(ReturnURL);  
}

and in your Ajax Post Method:

Onsuccess(function(retURL){ window.location(retURL); })

This will take to the new Action and that Action will return View.