gistfile1.cs

    public class Program
    {
        private static void Main()
        {
            var instance = new SomeClass
            {
                SomePropertyWithAttribute = "I have an attribute", 
                SomeProperty = "I don't have an attribute"
            };

            Inspect(instance);

            Console.ReadKey(false);
        }

        private static void Inspect(SomeClass instance)
        {
            var type = instance.GetType();
            foreach (var property in type.GetProperties())
            {
                var attribute = property.GetCustomAttributes(typeof(MyAttribute), false)
                    .Cast<MyAttribute>()
                    .FirstOrDefault();    

                if(attribute != null)
                {
                    Console.Out.WriteLine("{0} = {1}", attribute.GetType().Name, attribute.Value);
                }
                Console.Out.WriteLine("{0} = {1}", property.Name, property.GetValue(instance, null));
                Console.Out.WriteLine("");
            }
        }
    }

    public class SomeClass
    {
        public string SomeProperty { get; set; }

        [MyAttribute("MyValue")]
        public string SomePropertyWithAttribute { get; set; }
    }

    [AttributeUsage(AttributeTargets.Property)]
    public class MyAttribute : Attribute
    {
        public MyAttribute(string value)
        {
            Value = value;
        }

        public string Value { get; private set; }
    }