ASP.NET MVC ValidationAttribute Get Other Property Display Name

Question

I have created a custom CompareLessThan validation attribute by copying the ASP.NET MVC 3 CompareAttribute and instead of checking for equality, I check to see that one property is less than another. If there is a client side error, the message '{0} must be less than {1}' is displayed to the user.

My model is setup as follows with the Display attributes referencing a resource file.

[CompareLessThan("AmountAvailable", ErrorMessageResourceName="CompareLessThan", ErrorMessageResourceType = typeof(Resources.ValidationMessages))]
[Display(Name = "Amount", ResourceType = typeof(Resources.Labels))]
public decimal Amount { get; set; }

[Display(Name = "AmountAvailable", ResourceType = typeof(Resources.Labels))]
public decimal AmountAvailable { get; set; }

Then the custom validation GetClientValidationRules method is exactly the same as in the CompareAttribute

public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
{            
    yield return new ModelClientValidationLessThanRule(FormatErrorMessage(metadata.DisplayName), FormatPropertyForClientValidation(OtherProperty), this.AllowEquality);
}

Here we are generating the error message that will be displayed to the user if there is a problem. I can get the display name from the resource file for the property that is decorated with my custom CompareLessThan attribute, but my question is how do I go about getting the display name of the 'other' property we are comparing against? In the IsValid method we have a reference to the validationContext from which I can generate a PropertyInfo object for the 'other' property and I think get the display name. But, in the GetClientValidationRules I don't have access to that.

I could always just pass in another value for the display name of the other property but I was hoping there would be a way to derive it as I'm already specifying it with data annotations.

Any ideas?

Answer 1

As of ASP.NET MVC 4 this is how I managed to get the other property:

PropertyInfo otherPropertyInfo =
                  this.Metadata.ContainerType.GetProperty(attribute.DependentProperty);

Then I got the Display attribute from the property:

var displayAttribute =
    otherPropertyInfo.GetCustomAttributes(typeof(DisplayAttribute), true).
    FirstOrDefault() as DisplayProperty;

In your case:

// GetName() is important to get the translated name if you're using a resource file...
this.otherPropertyDisplayName = displayAttribute.GetName();

GetName() reference:

http://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.displayattribute.name%28v=vs.95%29.aspx