Define markup for [Required] fields in View in ASP.NET MVC 2.0

Question

We have a model with properties decorated with [Required] which works great for validation. However, what we'd like to do is mark those required fields in the view with an asterisk (or some other style) to denote they are required before the user enters any data for validation.

I don't seem to be able to find anything built into the MVC framework to allow me to do this and therefore wondered if anyone else had already solved this and how?

Ultimately what we're trying to prevent is the need to change code in two places if we subsequently remove a [Required] from a model property.

Many Thanks

Gregoire · Accepted Answer · 2010-06-04 14:40:19Z

4

You can build your own HtmlHelper extension for this:

public static string RequiredMarkFor<TModel, TValue>(this HtmlHelper html, Expression<Func<TModel, TValue>> expression)
{
    if(ModelMetadata.FromLambdaExpression(expression, html.ViewData).IsRequired)
         return "*";
    else
         return string.Empty;
}

answered Jun 4, 2010 at 14:40

Gregoire

24.9k7 gold badges50 silver badges74 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Stefanvds Over a year ago

I cant get this to work. the FromLambdaExpression gives an error about overload method...

Gregoire Over a year ago

Can you post the errors and your code (perhaps start a new topic)?

Stef Heyenrath · Accepted Answer · 2012-02-08 13:27:22Z

The problem with the solution from Gregoire and Faxanadu is that the "*" is always displayed, also when the field is validated using the normal validation and you use 'Html.ValidationMessageFor()'.

So if you use the html extension like this:

@Html.EditorFor(model => model.Email)
@Html.RequiredFieldFor(model => model.Email)
@Html.ValidationMessageFor(model => model.Email)

You'll see duplicate * in case the field has validation errors.

I've made this modified extension, based on this which does also check if the field was validated.

private static Type[] RequiredTypes = new Type[] { typeof(CustomRequiredAttribute), typeof(RequiredAttribute) };

/// <summary>
/// Generate a &lt;span class="field-validation-error"&gt;*&lt;&lt; element.
/// 
/// See http://koenluyten.blogspot.com/2011/06/denote-required-fields-in-aspnet-mvc-3.html
/// </summary>
public static MvcHtmlString RequiredFieldFor<TModel, TValue>(this HtmlHelper<TModel> html,
    Expression<Func<TModel, TValue>> expression, string validationMessage = "*")
{
    // Get the metadata for the model
    var metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);

    string fieldName = metadata.PropertyName;

    // Check if the field is required
    bool isRequired = metadata
        .ContainerType.GetProperty(fieldName)
        .GetCustomAttributes(false)
        .Count(m => RequiredTypes.Contains(m.GetType())) > 0;

    // Check if the field is validated
    bool isValidated = html.ViewData.ModelState[fieldName] != null;

    // If the field is required and not validated; generate span with an asterix
    if (isRequired && !isValidated)
    {
        var span = new TagBuilder("span");
        span.AddCssClass("field-validation-error");
        span.SetInnerText(validationMessage);

        return MvcHtmlString.Create(span.ToString(TagRenderMode.Normal));
    }

    return null;
}

Faxanadu · Accepted Answer · 2010-10-07 15:11:05Z

2

If you are getting an "invalid arguments" error when using "ModelMetadata.FromLambdaExpression", make sure you specify a generic type parameter for HtmlHelper. Here is a revised version of Gregoire's solution:

public static string RequiredMarkFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression)
    {
        if (ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData).IsRequired)
            return "*";
        else
            return string.Empty;
    }

answered Oct 7, 2010 at 15:11

Faxanadu

311 silver badge4 bronze badges

Comments

John Farrell · Accepted Answer · 2010-06-04 14:36:58Z

1

If you are using full form templated helpers EditorFor and DisplayFor you need to customize your own version of Object.ascx.

Brad Wilson has an awesome blog post which outlines this:

http://bradwilson.typepad.com/blog/2009/10/aspnet-mvc-2-templates-part-4-custom-object-templates.html

What happens it the IsRequired property on ModelMetadata will be true. Inside Object.ascx:

<%=propertu.IsRequired ? "*" : ""%>

If your not using templated helpers you'd have to write your own html helper. What do your views look like?

answered Jun 4, 2010 at 14:36

John Farrell

24.7k10 gold badges82 silver badges112 bronze badges

Comments

iuristona · Accepted Answer · 2012-06-27 14:37:20Z

0

I now the question is a little old, but I am working to an unobstrusive solution using just jquery.

My goal is to get all inputs marked with data-val-required attribute, and then set its label elementes markeds with attribute for

Here is the sample jquery code:

$('[data-val-required]').each(function() { 
    var $label = $('label[for=' + this.name + ']');

    //from here we can manipulate the label element
    $label.css('font-weight', 'bold');
    $label.text($label.text() + ' *');
});

edited Jun 27, 2012 at 14:37

answered Jun 27, 2012 at 14:30

iuristona

9271 gold badge13 silver badges30 bronze badges

Collectives™ on Stack Overflow

Define markup for [Required] fields in View in ASP.NET MVC 2.0

5 Answers 5

2 Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

2 Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related