How to change 'data-val-number' message validation in MVC while it is generated by @Html helper

Question

Assume this model:

Public Class Detail
    ...
    <DisplayName("Custom DisplayName")>
    <Required(ErrorMessage:="Custom ErrorMessage")>
    Public Property PercentChange As Integer
    ...
end class

and the view:

@Html.TextBoxFor(Function(m) m.PercentChange)

will proceed this html:

   <input data-val="true" 
    data-val-number="The field 'Custom DisplayName' must be a number." 
    data-val-required="Custom ErrorMessage"     
    id="PercentChange" 
    name="PercentChange" type="text" value="0" />

I want to customize the data-val-number error message which I guess has generated because PercentChange is an Integer. I was looking for such an attribute to change it, range or whatever related does not work.
I know there is a chance in editing unobtrusive's js file itself or override it in client side. I want to change data-val-number's error message just like others in server side.

Answer 1

This is not gonna be easy. The default message is stored as an embedded resource into the System.Web.Mvc assembly and the method that is fetching is a private static method of an internal sealed inner class (System.Web.Mvc.ClientDataTypeModelValidatorProvider+NumericModelValidator.MakeErrorString). It's as if the guy at Microsoft coding this was hiding a top secret :-)

You may take a look at the following blog post which describes a possible solution. You basically need to replace the existing ClientDataTypeModelValidatorProvider with a custom one.

If you don't like the hardcore coding that you will need to do you could also replace this integer value inside your view model with a string and have a custom validation attribute on it which would do the parsing and provide a custom error message (which could even be localized).