Range data annotation attribute does not validate .99?

Question

I have applied Range(decimal, decimal,...) to my property in model. It does not validate .99, but validates 0.99.

How to allow the leading Zero?

Answer 1

It is a bug in number regexp in jquery.validate.js and jquery.validate.min.js files that are by default coming with ASP.NET MVC 3.

Here is the code from jquery.validate.js, line 1048:

// http://docs.jquery.com/Plugins/Validation/Methods/number
number: function(value, element) {
    return this.optional(element) || /^-?(?:\d+|\d{1,3}(?:,\d{3})+)(?:\.\d+)?$/.test(value);
}

This function performs test of string against the number regular expression. To fix it, replace regexp with following one: /^-?(?:\d+|\d{1,3}(?:,\d{3})+)?(?:\.\d+)?$/.

This is a short version. Now here is the explanation:

Buggy ^-?(?:\d+|\d{1,3}(?:,\d{3})+)(?:\.\d+)?$ regexp reads as:

^-?
  Beginning of line or string
  -, zero or one repetitions
Match expression but don't capture it. [\d+|\d{1,3}(?:,\d{3})+]
  Select from 2 alternatives
      Any digit, one or more repetitions
      \d{1,3}(?:,\d{3})+
          Any digit, between 1 and 3 repetitions
          Match expression but don't capture it. [,\d{3}], one or more repetitions
              ,\d{3}
                  ,
                  Any digit, exactly 3 repetitions
Match expression but don't capture it. [\.\d+], zero or one repetitions
  \.\d+
      Literal .
      Any digit, one or more repetitions
End of line or string

As you can see, second capturing group (?:\.\d+)? allows numbers in .XX format but when matching, first group (?:\d+|\d{1,3}(?:,\d{3})+) is checked first and validation fails because first group must be matched.

If we will reffer to the http://docs.jquery.com/Plugins/Validation/Methods/number demo and examine their regexp for number validation it will look as follows: ^-?(?:\d+|\d{1,3}(?:,\d{3})+)?(?:\.\d+)?$. Which is same as buggy one but now first matching group should be of zero or one repetitions or optional in other words. And this additional ? in regexp fixes bug.

Edit: this also applies to MVC 4 default template. Both templates are using 1.9.0 version of plugin. In version 1.10.0 this issue was fixed. From changelog:

• Fixed regex issue for decimals without leading zeroes. Added new methods test. Fixes #41

So sometimes staying updated is a good idea.