MaxLength Attribute not generating client-side validation attributes

Question

I have a curious problem with ASP.NET MVC3 client-side validation. I have the following class:

public class Instrument : BaseObject
{
    public int Id { get         


        

Answer 1

<input class="text-box single-line" data-val="true" data-val-required="Name is required." 
    id="Name1" name="Name" type="text" value="">

$('#Name1').keypress(function () {
    if (this.value.length >= 5) return false;
});

Answer 2

Try using the [StringLength] attribute:

[Required(ErrorMessage = "Name is required.")]
[StringLength(40, ErrorMessage = "Name cannot be longer than 40 characters.")]
public string Name { get; set; }

That's for validation purposes. If you want to set for example the maxlength attribute on the input you could write a custom data annotations metadata provider as shown in this post and customize the default templates.

Answer 3

In MVC 4 If you want maxlenght in input type text ? You can !

@Html.TextBoxFor(model => model.Item3.ADR_ZIP, new { @class = "gui-input ui-oblig", @maxlength = "5" })

Answer 4

StringLength works great, i used it this way:

[StringLength(25,MinimumLength=1,ErrorMessage="Sorry only 25 characters allowed for 
              ProductName")]
public string ProductName { get; set; }

or Just Use RegularExpression without StringLength:

[RegularExpression(@"^[a-zA-Z0-9'@&#.\s]{1,25}$", ErrorMessage = "Reg Says Sorry only 25 
                   characters allowed for ProductName")]    
public string ProductName { get; set; }

but for me above methods gave error in display view, cause i had already ProductName field in database which had more than 25 characters

so finally i came across this and this post and tried to validate without model like this:

 <div class="editor-field">
 @Html.TextBoxFor(model => model.ProductName, new
 {
 @class = "form-control",
 data_val = "true",
 data_val_length = "Sorry only 25 characters allowed for ProductName",
 data_val_length_max = "25",
 data_val_length_min = "1"
 })
 <span class="validation"> @Html.ValidationMessageFor(model => model.ProductName)</span>
 </div>

this solved my issue, you can also do validation manually using jquery or using ModelState.AddModelError

hope helps someone.

Answer 5

I know I am very late to the party, but I finaly found out how we can register the MaxLengthAttribute.

First we need a validator:

public class MaxLengthClientValidator : DataAnnotationsModelValidator<MaxLengthAttribute>
{
    private readonly string _errorMessage;
    private readonly int _length;


    public MaxLengthClientValidator(ModelMetadata metadata, ControllerContext context, MaxLengthAttribute attribute)
    : base(metadata, context, attribute)
    {
        _errorMessage = attribute.FormatErrorMessage(metadata.DisplayName);
        _length = attribute.Length;
    }

    public override IEnumerable<ModelClientValidationRule> GetClientValidationRules()
    {
        var rule = new ModelClientValidationRule
        {
            ErrorMessage = _errorMessage,
            ValidationType = "length"
        };

        rule.ValidationParameters["max"] = _length;
        yield return rule;
    }
}

Nothing realy special. In the constructor we save some values from the attribute. In the GetClientValidationRules we set a rule. ValidationType = "length" is mapped to data-val-length by the framework. rule.ValidationParameters["max"] is for the data-val-length-max attribute.

Now since you have a validator, you only need to register it in global.asax:

protected void Application_Start()
{
    //...

    //Register Validator
    DataAnnotationsModelValidatorProvider.RegisterAdapter(typeof(MaxLengthAttribute), typeof(MaxLengthClientValidator));
}

Et voila, it just works.