ASP.NET MVC ValidationAttribute Get a different display property name

Question

I created my own CompareLessThan validation attribute by copying ASP.NET MVC 3 CompareAttribute and instead of checking for equality, I verify that one property is smaller than the other. If there is an error on the client side, the message "{0} must be less than {1}" is displayed to the user.

My model is configured as follows with 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 GetClientValidationRules spot check method is exactly the same as in CompareAttribute

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

Here we create an 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 CompareLessThan custom attribute, but my question is, how can I get the display name of the “other” property with which we are comparing? In the IsValid method, we refer to a validationContext from which I can generate a PropertyInfo object for the "other" property, and I think I get the display name. But in GetClientValidationRules I do not have access to this.

I could always just pass a different value for the display name of another property, but I was hoping there would be a way to get it, as I already specify it with data annotations.

Any ideas?

Answer 1

The answer provided by nemesv does not work as the metadata.Model property is 0. But through the metadata we have the full name of the model, so you can create a new instance of this model and then create a new DataAnnonationsModelMetadataProvider from this create instance. From there we can get the display name of another property.

 public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context) { Type type = Type.GetType(metadata.ContainerType.FullName); var model = Activator.CreateInstance(type); var provider = new DataAnnotationsModelMetadataProvider(); var otherMetaData = provider.GetMetadataForProperty(() => model, type, this.OtherProperty); this.otherPropertyDisplayName = otherMetaData.DisplayName; yield return new ModelClientValidationLessThanRule(FormatErrorMessage(metadata.DisplayName), FormatPropertyForClientValidation(this.OtherProperty), this.AllowEquality); } 

I really don't like this solution (although it works), as it seems there should be a better way. Does anyone have any other ideas?

Answer 2

As in ASP.NET MVC 4, I managed to get another 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() link:

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

Answer 3

I have not tried, but you can get the model properties using the metadata.Properties property

 metadata.Properties.Single(p => p.PropertyName == "OtherPropName").DisplayName; 

EDIT: since the properties are empty, you can always do it (albeit very elegantly). You can generate metadata for yourself.

 var provider = new DataAnnotationsModelMetadataProvider(); var otherMetaData = provider.GetMetadataForProperty(() => metaData.Model, metaData.ModelType, "OtherPropertyName");