title: radio button validation not working asp.net core 3.1
body: <p>I have three input filed (text - tow radio button) for one property asp-validation-for works only for the input text I want to validate radio button also if it is not checked ,Model :</p>
  
  <pre><code>        [BindProperty,Required(ErrorMessage = "Required")]
           public string PriceAfter { get; set; } 
  </code></pre>
  
  <p>Index.cshtml :</p>
  
  <pre><code>                         &lt;div class="form-group"&gt;                    
                                  &lt;input type="number" class="form-control" 
                                         asp-for="Ad.PriceAfter"&gt;
                                  &lt;label class="custom-control custom-radio mb-2 ml-4"&gt;
                                      &lt;input type="radio" class="custom-control-input" 
                                              value="new" asp-for="Ad.PriceAfter"  id="PriceAfter"&gt;
                                      &lt;span class="custom-control-label"&gt;&lt;a href="#" class="text-muted"&gt;new&lt;/a&gt;&lt;/span&gt;
                                  &lt;/label&gt;
                                  &lt;label class="custom-control custom-radio  mb-2"&gt;
                                      &lt;input type="radio" class="custom-control-input" 
                                             value="Used" asp-for="Ad.PriceAfter" id="PriceAfter"&gt;
                                      &lt;span class="custom-control-label"&gt;
                                          &lt;a href="#" class="text-muted"&gt;Used &lt;/a&gt;&lt;/span&gt;
  
                                  &lt;/label&gt;
                                  &lt;span asp-validation-for="Ad.PriceAfter" class="text-danger"&gt;&lt;/span&gt;
                          &lt;/div&gt;
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/EWaAX.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EWaAX.jpg" alt="Design"></a></p>