MVC 4 - DataAnnotations - Validation for Type

You can try with the regular expression:

[RegularExpression(@"[0-9]*\.?[0-9]+", ErrorMessage = "{0} must be a Number.")]

you can also try the Data Annotations Extensions:http://dataannotationsextensions.org/Home/Wiki

Or write your own implementation,something like this :https://github.com/srkirkland/DataAnnotationsExtensions/blob/master/DataAnnotationsExtensions/DigitsAttribute.cs

UPDATEWith REGEX (Matches $9,999.99 | $0.70 | .1)

[RegularExpression(@"^\$?([1-9]{1}[0-9]{0,2}(\,[0-9]{3})*(\.[0-9]{0,2})?|[1-9]{1}[0-9]{0,}(\.[0-9]{0,2})?|0(\.[0-9]{0,2})?|(\.[0-9]{1,2})?)$", ErrorMessage = "{0} must be a Number.")]

Or using Range with a slight modification to @Martin suggestion (actually is a better solution):

[Range(typeof(Decimal), "0", "9999", ErrorMessage = "{0} must be a decimal/number between {1} and {2}.")]

First off, I think you will want to change your Range attribute to

[Range(typeof(Decimal), "1", "9999", ErrorMessage = "{0} must be a decimal/number between {1} and {2}.")]

According to MSDN, this is the valid way to use RangeAttribute.

Second:

"The field productPrice must be a number."

This is actually unobtrusive client-side JavaScript validation kicking in. Your range validator will fire after the number has been validated. You can disable the number validator although I do not recommend this:

$.validator.methods.number = function (n, t) {    return true;}

I think you may be tripping over a bug in jQuery. That validation is fighting the stuff emitted for your validation attributes.

I have the following property:

[Display(ResourceType = typeof(TaxSetupResources), Name = "Model_Value")][RegularExpression(@"(^\d+$)|(^\.\d{1,4}$)|(^\d*\.\d{0,4}$)", ErrorMessageResourceName="Model_InvalidFormatForAmount", ErrorMessageResourceType=typeof(TaxSetupResources))]public decimal? Value { get; set; }

Used in a view like this:

<div>    @Html.TextBoxFor(t => t.Tiers[i].Value, new { title = @Resources.TaxSetupResources.Model_ValueTip })    <br />@Html.ValidationMessageFor(t => t.Tiers[i].Value)</div>

Just by itself, a value "foo" yields my error message. A value 0.075 is accepted. A value of .075 yields "The field Value must be a number", the same issue you seem to be having.

based on this SO article, I added the following in document ready:

$(function () {    $.validator.methods.number = function (value, element) {        return parseFloat(value).toString() !== "NaN";    }});

Now I only get my error message, and only when expected (.075 is accepted).