how to change image in razor page in asp.net core 2

Question

I have some logic in C#, that controls which image I should show on a webpage.

basically I want to update the image, when a button is pushed, but I want to do it in the controller of a razor page. And not I javascript or html, where it is fairly simple.

I am thinking somehow along the lines of: // the controller

 public class APageController {
    ...
    public IActionResult AButtonPushed() {
       bool yes;
       ...
       // some logic that changes yes 
       ...
       aPageModel.ImagePath = yes               // how do I access the 
                         ? "\images\true.jpg"   // razor view class from 
                         : "\images\ohNooo.jpg" // controller
      return RedirectToPage("/aPage");
      }
    ... 
 }

// the razor page model

  public class aPageModel : PageModel {
    ... 
    public string ImagePath {get;set;}
    ... 
 }

// and the razor page html

   ...
   < img src="@Model.ImagePath"/>
   ...

or it maybe I should use some helper tag, to force the page to react to the change of imagePath in the PageModel.