Checking attributes on classes can be done by getting the type of the class and executing GetCustomAttributes() on it. You just need to iterate over the resulting object[] to find what you are interested in.

To simplify this a bit more, I wrote a couple of extension methods :

    static public class AttributeExtensions
    {
        static public T FindAttribute<T>(this object obj)
            where T : Attribute
        {
            return obj.GetType().GetCustomAttributes(true)
                .Where(attr => attr.GetType() == typeof(T))
                .Select(attr => attr as T).FirstOrDefault();
        }

        static public List<Attribute> GetAttributes(this object obj)
        {
            return obj.GetType().GetCustomAttributes(true).ConvertAllItems(c => c as Attribute).ToList();
        }

        static private IEnumerable<TOutput> ConvertAllItems<TInput, TOutput>(this IEnumerable<TInput> e, 
            Converter<TInput, TOutput> op)
        {
            foreach (TInput item in e)
            {
                yield return op(item);
            }
        }
    }

So, on a Person class like this

    [DataContract(Namespace="http://www.u2u.be/demo/entities")]
    public class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }
    }

    Person p = new Person() { Name = "John Doe", Age = 77 } ;

You can now find the DataContractAttribute by:

    DataContractAttribute attribute = p.FindAttribute<DataContractAttribute>();
    Console.WriteLine(attribute != null ? attribute.Namespace : "Attribute not found");

Or, to retrieve the list of attributes:

    List<Attribute> lst = p.GetAttributes();