Attribute querying not casting to base type of attribute, what gives?!?

Question

I'm trying to query attributes and access the base type of several attributes. For some reason it is failing to cast properly and not executing as expected. Here is the code below:

    internal static void ValidateProperties(TModel model, ModelStateDictionary modelState)
    {
        Type type = model.GetType();            
        PropertyInfo[] properties = type.GetProperties();
        foreach (PropertyInfo property in properties)
        {                
            foreach(Attribute attribute in property.GetCustomAttributes(true))
            {
                ValidationAttribute validationAttribute = attribute as ValidationAttribute;
                if (validationAttribute != null)
                {                        
                    if (!validationAttribute.IsValid(property.GetValue(model, null)))
                        modelState.AddModelError(property.Name, validationAttribute.ErrorMessage);
                }
            }
        }            
    } 

For some reason validateAttribute is always null. In debugging it won't cast CustomValidationAttribute or RequiredAttribute. Trying to directly cast to ValidationAttribute instead of using the "as" keyword results in an Invalid Cast exception for both of these types as well. Clearly they are derived from ValidationAttribute: http://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.validationattribute.aspx

What am I missing? Thanks!

---

Edit: Per request, I've added an Debug statement to output the Type of the Attribute. The results are as follows:

System.ComponentModel.DataAnnotations.CustomValidationAttribute System.ComponentModel.DataAnnotations.RequiredAttribute System.ComponentModel.DataAnnotations.RegularExpressionAttribute System.ComponentModel.DataAnnotations.CustomValidationAttribute System.ComponentModel.DataAnnotations.RequiredAttribute

Answer 1

EDIT:

Before actually casting please do type-check for Attribute.

Instead of directly casting..

ValidationAttribute validationAttribute = attribute as ValidationAttribute;

Check..

if(!(attribute is ValidationAttribute))
{
    continue;
}
ValidationAttribute validationAttribute = attribute as ValidationAttribute;

Original:

This is how you can do this.

Why iterate through all attributes of a property, instead filter all properties having attribute of type ValidationAttribute.

        PropertyInfo[] properties = model.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance);

        var valProps = from PropertyInfo property in properties
                       where property.GetCustomAttributes(typeof(ValidationAttribute), true).Length > 0
                       select new
                       {
                           Property = property,
                           ValidationAttributes = property.GetCustomAttributes(typeof(ValidationAttribute), true)
                       };

        foreach (var item in valProps)
        {
            foreach (ValidationAttribute attribute in item.ValidationAttributes)
            {
                if (attribute.IsValid(item.Property.GetValue(model, null)))
                {
                    continue;
                }

                //Validation fails..
            }
        }
    }

Answer 2

It doesn't look like you're missing anything or doing anything wrong, so here's a shot in the dark: are the assemblies (the one querying and the one being queried) using different (strong-named) versions of the System.ComponentModel.DataAnnotations.dll?