How to add required attribute to mvc razor viewmodel text input editor

Question

I have the following MVC 5 Razor HTML helper    Html TextBoxFor m   gt  m ShortName     new    class    form-control    placeholder    short name      I need this field to be required  i e  have a red outline when user navigates out without putting a value inn   In a WebForms HTML 5 I could just say  lt input type  text  required   gt  to have this effect  What is the proper syntax to accomplish this in a Razor syntax

User · Answer

Erik s answer didn t fly for me    Following did     Html TextBoxFor m   gt  m ShortName   new   data val required    You need me       plus doing this manually under field I had to add error message container   Html ValidationMessageFor m   gt  m ShortName  null  new    class    field-validation-error   data valmsg for    ShortName       Hope this saves you some time

User · Answer

On your model class decorate that property with  Required  attribute  I e     Required  public string ShortName  get  set

User · Answer

A newer way to do this in  NET Core is with TagHelpers    https   docs microsoft com en-us aspnet core mvc views tag-helpers intro  Building on these examples  MaxLength  Label   you can extend the existing TagHelper to suit your needs   RequiredTagHelper cs  using Microsoft AspNetCore Razor TagHelpers  using System ComponentModel DataAnnotations  using System Collections Generic  using Microsoft AspNetCore Mvc ViewFeatures  using System Linq   namespace ProjectName TagHelpers        HtmlTargetElement  input   Attributes    asp-for        public class RequiredTagHelper   TagHelper               public override int Order                       get   return int MaxValue                        HtmlAttributeName  asp-for            public ModelExpression For   get  set             public override void Process TagHelperContext context  TagHelperOutput output                        base Process context  output                 if  context AllAttributes  required      null                                var isRequired   For ModelExplorer Metadata ValidatorMetadata Any a   gt  a is RequiredAttribute                   if  isRequired                                        var requiredAttribute   new TagHelperAttribute  required                        output Attributes Add requiredAttribute                                                       You ll then need to add it to be used in your views    ViewImports cshtml   using ProjectName  addTagHelper    Microsoft AspNetCore Mvc TagHelpers  addTagHelper     ProjectName    Given the following model   Foo cs  using System  using System ComponentModel DataAnnotations   namespace ProjectName Models       public class Foo               public int Id   get  set              Required           Display Name    Full Name            public string Name   get  set              and view  snippet    New cshtml   lt label asp-for  Name  gt  lt  label gt   lt input asp-for  Name   gt    Will result in this HTML    lt label for  Name  gt Full Name lt  label gt   lt input required type  text  data-val  true  data-val-required  The Full Name field is required   id  Name  name  Name  value     gt    I hope this is helpful to anyone with same question but using  NET Core

User · Answer

I needed the  required  HTML5 atribute  so I did something like this    lt    Html TextBoxFor model   gt  model Name  new    required   true     gt

User · Answer

You can use the required html attribute if you want    Html TextBoxFor m   gt  m ShortName   new    class    form-control   placeholder    short name   required  required      or you can use the RequiredAttribute class in  Net  With jQuery the RequiredAttribute can Validate on the front end and server side   If you want to go the MVC route  I d suggest reading Data annotations MVC3 Required attribute   OR  You can get really advanced           if you aren t using UnobtrusiveValidation  don t pass anything to this constructor   var attributes   new Dictionary lt string  object gt       Html GetUnobtrusiveValidationAttributes ViewData TemplateInfo HtmlFieldPrefix      attributes Add  class    form-control     attributes Add  placeholder    short name       if  ViewData ModelMetadata ContainerType        GetProperty ViewData ModelMetadata PropertyName         GetCustomAttributes typeof RequiredAttribute   true         Select a   gt  a as RequiredAttribute         Any a   gt  a    null          attributes Add  required    required            Html TextBoxFor m   gt  m ShortName  attributes       or if you need it for multiple editor templates   public static class ViewPageExtensions     public static IDictionary lt string  object gt  GetAttributes this WebViewPage instance             if you aren t using UnobtrusiveValidation  don t pass anything to this constructor     var attributes   new Dictionary lt string  object gt         instance Html GetUnobtrusiveValidationAttributes           instance ViewData TemplateInfo HtmlFieldPrefix         if  ViewData ModelMetadata ContainerType        GetProperty ViewData ModelMetadata PropertyName         GetCustomAttributes typeof RequiredAttribute   true         Select a   gt  a as RequiredAttribute         Any a   gt  a    null               attributes Add  required    required                  then in your templates           if you aren t using UnobtrusiveValidation  don t pass anything to this constructor   var attributes   this GetAttributes       attributes Add  class    form-control      attributes Add  placeholder    short name        Html TextBoxFor m   gt  m ShortName  attributes       Update 1  for Tomas who is unfamilar with ViewData     What s the difference between ViewData and ViewBag   Excerpt      So basically it  ViewBag  replaces magic strings   ViewData  Foo         with magic properties   ViewBag Foo

[asp.net-mvc] How to add "required" attribute to mvc razor viewmodel text input editor

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