[asp.net-mvc] DataAnnotations validation (Regular Expression) in asp.net mvc 4 - razor view

The DataAnnotations validator not working in asp.net mvc 4 razor view, when using the special characters in the regular expression.

Model:

[StringLength(100)]
[Display(Description = "First Name")]
[RegularExpression("^([a-zA-Z0-9 .&'-]+)$", ErrorMessage = "Invalid First Name")]
public string FirstName { get; set; }

Razor View:

@Html.TextBoxFor(model => Model.FirstName, new { })
@Html.ValidationMessageFor(model => Model.FirstName)

The unobtrusive validation is rendered in view as:

<input type="text" value="" tabindex="1" style="height:auto;" name="FirstName" maxlength="100" id="FirstName" data-val-regex-pattern="^([a-zA-Z0-9 .&amp;amp;&amp;#39;-]+)$" data-val-regex="Invalid First Name" data-val-length-max="100" data-val-length="The field FirstName must be a string with a maximum length of 100." data-val="true" class="textfield ui-input-text ui-body-d ui-corner-all ui-shadow-inset valid">

The regex pattern in the above html is not rendered as specified in the Model's RegularExpression, which results in error even when entering the valid data (Sam's).

How can i handle this?

--UPDATE--

I have updated the code as per @Rick suggestion

[StringLength(100)]
[Display(Description = "First Name")]
[RegularExpression("([a-zA-Z0-9 .&'-]+)", ErrorMessage = "Enter only alphabets and numbers of First Name")]
public string FirstName { get; set; }

View Source shows the following:

<input data-val="true" data-val-length="The field FirstName must be a string with a maximum length of 100." data-val-length-max="100" data-val-regex="Enter only alphabets and numbers of First Name" data-val-regex-pattern="([a-zA-Z0-9 .&amp;amp;&amp;#39;-]+)" id="FirstName" maxlength="100" name="FirstName" type="text" value="" />

Still i have the same issue.

What browser are you using? I entered your example and tried in both IE8 and Chrome and it validated fine when I typed in the value Sam's

 public class IndexViewModel
 {
    [Required(ErrorMessage="Required")]
    [RegularExpression("^([a-zA-Z0-9 .&'-]+)$", ErrorMessage = "Invalid First Name")]
    public string Name { get; set; }
 }

When I inspect the DOM using IE Developer toolbar and Chrome Developer mode it does not show any special characters.

This one worked for me, try this

[RegularExpression("^[a-zA-Z &\-@.]*$", ErrorMessage = "--Your Message--")]

Try escaping those characters:

[RegularExpression(@"^([a-zA-Z0-9 \.\&\'\-]+)$", ErrorMessage = "Invalid First Name")]

Try @ sign at start of expression. So you wont need to type escape characters just copy paste the regular expression in "" and put @ sign. Like so:

[RegularExpression(@"([a-zA-Z\d]+[\w\d]*|)[a-zA-Z]+[\w\d.]*", ErrorMessage = "Invalid username")]
public string Username { get; set; }

We've had similar issue in the past (as mentioned by TweeZz). In our case we're controlling outputting of TextBoxFor by our custom htmlHelper extension method which is building MvcHtmlString, there in one step we need to add these unobtrusive validation attributes, which is done via

var attrs = htmlHelper.GetUnobtrusiveValidationAttributes(name, metadata)

after call to this method, attributes are html encoded, so we simply check if there was Regular expression validator there and if so, we html unencode this attribute and then merge them into tagBuilder (for building "input" tag)

if(attrs.ContainsKey("data-val-regex"))
    attrs["data-val-regex"] = ((string)attrs["data-val-regex"]).Replace("&","&");
tagBuilder.MergeAttributes(attrs);

We only cared about & amps, that's why this literal replacement

Try this one in model class

    [Required(ErrorMessage = "Enter full name.")]
    [RegularExpression("([A-Za-z])+( [A-Za-z]+)", ErrorMessage = "Enter valid full name.")]

    public string FullName { get; set; }

Try using the ASCII code for those values:

^([a-zA-Z0-9 .\x26\x27-]+)$

• \x26 = &
• \x27 = '

The format is \xnn where nn is the two-digit hexadecimal character code. You could also use \unnnn to specify a four-digit hex character code for the Unicode character.

The problem is that the regex pattern is being HTML encoded twice, once when the regex is being built, and once when being rendered in your view.

For now, try wrapping your TextBoxFor in an Html.Raw, like so:

@Html.Raw(Html.TextBoxFor(model => Model.FirstName, new { }))