FormController.cs

gistfile1.cs

protected ActionResult Handle<TForm, TResult>(TForm form,
    Func<TResult, ActionResult> successResultGetter,
    Func<ActionResult> failResultGetter) where TForm : IForm
{
    if (ModelState.IsValid)
    {
        try
        {
            var result = FormHandlerFactory.Create<TForm, TResult>().Handle(form);

            return successResultGetter(result);
        }
        catch (Exception e)
        {
            ModelState.AddModelError("", e.Message);
        }
    }

    TempData[ModelStateKey] = ModelState;
    TempData[ValueProviderKey] = ValueProvider; 
    return failResultGetter();
}

IFormHandler`2.cs

public interface IFormHandler<in TForm, out TResult> where TForm : IForm
{
    TResult Handle(TForm form);
}