Add demo to prove fix works

Author: haacked

Controllers/Validations.cs

@@ -10,6 +10,12 @@ public IActionResult CheckRemote(string id)
         return Ok(id == "42");
     }
 
+    [HttpPost]
+    public IActionResult CheckboxRemote(bool isChecked)
+    {
+        return Ok(isChecked);
+    }
+
     [HttpGet]
     public IActionResult Test()
     {

Pages/Demos/Checkboxes.cshtml

@@ -52,8 +52,8 @@
                 <label>@animal</label>
             }
             <span asp-validation-for="SelectedAnimals"></span>
-            @if (Model.SelectedAnimals.Any()) {
-                <em class="results">Selected animals: @string.Join(", ", Model.SelectedAnimals)</em>
+            @if (Model.SelectedAnimals!.Any()) {
+                <em class="results">Selected animals: @string.Join(", ", Model.SelectedAnimals!)</em>
             }
         </div>
 

Pages/Demos/Checkboxes.cshtml.cs

@@ -41,6 +41,7 @@ public IActionResult OnPost()
 
     public class InputModel
     {
+        [Remote("CheckboxRemote", "Validations", HttpMethod = "Post")]
         public bool IsChecked { get; set; }
     }
 
@@ -50,6 +51,7 @@ public class InputModel
     public class Selectable
     {
         public required string Name { get; set; }
+
         public bool IsSelected { get; set; }
     }
 }