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Is the DataTypeAttribute validation working in MVC2?

Answer 1

+4 A:

Like LukLed pointed out, DataTypeAttribute doesn't do any validation by default. But it does influence templates regarding how the data is presented.

For example if you call Html.DisplayFor() method on a model that has DataType(DataType.EmailAddress) attribute, it'll format its value with <a href="mailto:{0}">{0}</a> (at least in MVC RC2).

çağdaş 2010-03-06 06:07:00

Thanks for point out that DataTypeAttribute is not a validation attribute.

Wen Q. 2010-03-06 06:17:03

@Wayne: It actually is ValidationAttribute. It inherits from ValidationAttribute, but always returns true. You can override IsValid method and define your own, as it is in David Hayden's solution.

LukLed 2010-03-06 06:19:01

@LukLed, It indeed inherits from ValidationAttribute. I wonder why. Anyway, will correct that part.

çağdaş 2010-03-06 06:24:29

@çağdaş: `DataAnnotationsModelValidator` goes through every ValidationAttribute. DataTypeAttribute is ValidationAttribute, so it could be easily inherited and validation introduced. When you define your own data type, you can easily add validation.

LukLed 2010-03-06 06:31:16

@LukLed, Thanks. I edited the answer again to delete the part where it said it's not used for validation.

çağdaş 2010-03-06 06:45:19

Answer 2

+5 A:

[DataType("EmailAddress")] doesn't influence validation by default. This is IsValid method of this attribute (from reflector):

public override bool IsValid(object value)
{
    return true;
}

This is example of custom DataTypeAttribute to validate Emails (taken from this site http://davidhayden.com/blog/dave/archive/2009/08/12/CustomDataTypeAttributeValidationCustomDisplay.aspx):

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple  = false)]
public class EmailAddressAttribute : DataTypeAttribute
{
    private readonly Regex regex = new Regex(@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*", RegexOptions.Compile

    public EmailAddressAttribute() : base(DataType.EmailAddress)
    {

    }

    public override bool IsValid(object value)
    {

        string str = Convert.ToString(value, CultureInfo.CurrentCulture);
        if (string.IsNullOrEmpty(str))
            return true;

        Match match = regex.Match(str);   
        return ((match.Success && (match.Index == 0)) && (match.Length == str.Length));
    }
}

LukLed 2010-03-06 06:08:08

Thanx for this.

George Handlin 2010-04-13 12:44:28

I think you want to make that regex static because setting the compiled option may cause compilation to be done everwhere the attribute is used and, if memory serves, generating a new in-memory assembly each time.

Mike Scott 2010-05-31 17:45:42

@Mike Scott: New in-memory assembly? What do you mean by that?

LukLed 2010-05-31 21:32:19

LukLed, what it says on the tin - an assembly created on the fly in memory ;-) Regex with the compiled option emits IL into an in-memory assembly. So to be sure you don't use up memory with each invocation, you should save the compiled regex instance and reuse it. see http://blogs.msdn.com/b/bclteam/archive/2004/11/12/256783.aspx.

Mike Scott 2010-06-02 17:53:46

Answer 3

A:

Check out Scott Guthrie's blog post on MVC 2 validation. It is excellent. http://weblogs.asp.net/scottgu/archive/2010/01/15/asp-net-mvc-2-model-validation.aspx

Rick 2010-04-14 01:37:40

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