Question

I’m just getting started with ASP.NET MVC 2, and playing around with Validation.

Let’s say I have 2 properties:

• Password1
• Password2

And I want to require that they are both filled in, and require that both are the same before the model is valid.

I have a simple class called “NewUser”.

How would I implement that? I’ve read about ValidationAttribute, and understand that. But I don’t see how I would use that to implement a validation that compares two or more properties against eathother.

Thanks in advance!

Problem with below solution:

When this is applied to an application, and the ModelBinder runs the validation of the Model, then there is a problem:

If a Property-level ValidationAttribute contains an error, then the Class-level ValidationAttribute‘s are NOT validated. I have not found a solution to this problem as of yet.

If you have a solution to this problem please share your experience. Thanks alot!

Answer 1

The default ASP.NET MVC 2 template of Visual Studio includes the exact validation attribute you need. Pasted from AccountModels.cs file :

[AttributeUsage(AttributeTargets.Class, 
    AllowMultiple = true, Inherited = true)]
public sealed class PropertiesMustMatchAttribute : ValidationAttribute {
    private const string _defaultErrorMessage = 
        "'{0}' and '{1}' do not match.";
    private readonly object _typeId = new object();

    public PropertiesMustMatchAttribute(string originalProperty, 
        string confirmProperty)
        : base(_defaultErrorMessage) {
        OriginalProperty = originalProperty;
        ConfirmProperty = confirmProperty;
    }

    public string ConfirmProperty { get; private set; }
    public string OriginalProperty { get; private set; }

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

    public override string FormatErrorMessage(string name) {
        return String.Format(CultureInfo.CurrentUICulture, ErrorMessageString,
            OriginalProperty, ConfirmProperty);
    }

    public override bool IsValid(object value) {
        PropertyDescriptorCollection properties = 
           TypeDescriptor.GetProperties(value);
        object originalValue = properties.Find(OriginalProperty, 
            true /* ignoreCase */).GetValue(value);
        object confirmValue = properties.Find(ConfirmProperty, 
            true /* ignoreCase */).GetValue(value);
        return Object.Equals(originalValue, confirmValue);
    }
}

How to use :

[PropertiesMustMatch("Password", "ConfirmPassword", 
    ErrorMessage = "The password and confirmation password do not match.")]
class NewUser {
    [Required]
    [DataType(DataType.Password)]
    [DisplayName("Password")]
    public string Password { get; set; }
    [Required]
    [DataType(DataType.Password)]
    [DisplayName("Confirm password")]
    public string ConfirmPassword { get; set; }
}