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Answer 1

+1 A:

try this

[AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = true)]
public sealed class EitherOr : ValidationAttribute
{
    private const string _defaultErrorMessage = "'{0}' OR '{1}' OR '{2}' must have a value";
    private readonly object _typeId = new object();

    public EitherOr(string prop1, string prop2, string prop3)
        : base(_defaultErrorMessage)
    {
        Prop1 = prop1;
        Prop2 = prop2;
        Prop3 = prop3;

    }

    public string Prop1 { get; private set; }
    public string Prop2 { get; private set; }
    public string Prop3 { get; private set; }

    public override object TypeId
    {
        get
        {
            return _typeId;
        }
    }

    public override string FormatErrorMessage(string name)
    {
        return String.Format(CultureInfo.CurrentUICulture, ErrorMessageString, Prop1, Prop2,Prop3);
    }

    public override bool IsValid(object value)
    {
        if(string.IsNullOrEmpty(Prop1)&&string.IsNullOrEmpty(Prop2) && string.IsNullOrEmpty(Prop3))
        {
            return false;
        }
        return true;
    }

then mark your class with the EitherOr attribute:

[EitherOr("Bar","Stool","Hood", ErrorMessage = "please supply one of the properties")]
    public class Foo
    {
        public string Bar{ get; set;}
        public string Stool{ get; set;}
        public string Hood{ get; set;}
    }

Please note that i made use of string properties, if your property is of other type, makle sure to change the IsValid(object value) validation

Dusty Roberts 2010-09-22 15:35:13

Thanks Dusty, what javacript validation script should I write in this case? should I still implement DataAnnotationsModelValidator and register it?

byte 2010-09-22 15:39:37

You shouldn't have to write any javascript if you use the default `Html.ValidationSummary`. the error messagfe will be displayed in your validation summary. however, if you want it displayed next to each of the form fields you will have to make use of: ModelState.AddModelError("Bar", "requires a value");

Dusty Roberts 2010-09-22 15:55:09

Thanks. Does this validation happen at server side then? I am looking at input validation on client side as well to give better UI and avoid server trip where possible. Server side validation will always be around.

byte 2010-09-22 15:58:29

You can enable clientside validation on mvc2, have a look here http://dotnetaddict.dotnetdevelopersjournal.com/clientvalidation_mvc2.htm, it will validate against your model and it's appropriate data annotations

Dusty Roberts 2010-09-22 16:39:15

Also take note that if you go the ModelState.AddModelError route you will have to validate server side

Dusty Roberts 2010-09-22 16:41:52

Dusty, Looks like I have to use reflection. I used your example and in IsValid I see the values of Prop1 = "Bar" and not the value of "Bar"

byte 2010-09-27 08:48:05

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asp.net mvc2 validations

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