MVC ModelState.AddModelError use

 

cshtml: The red part   is the field using the method PostNextDay

 <div id="postNextDay" class="col-xs-12 col-sm-6 col-md-4">
                                <div class="form-group checkbox">
                                    @Html.CheckBoxFor(m => m.PostNextDay)
                                    @Html.LabelFor(m => m.PostNextDay)
                                    @Html.ValidationMessageFor(m => m.PostNextDay)
                                </div>
                            </div>

You can write verification in the Controller to control, the first parameter key and the second parameter prompt the content

  ModelState.AddModelError( " PostNextDay " , $ "Write prompt content here " );