attribute?.Description是什么意思？

   public static string GetDescription(Enum value, Boolean nameInstead = true) {

            try {

                Type type = value.GetType();

                string name = Enum.GetName(type, value);

                if (name == null) {

                    return null;

                }



                System.Reflection.FieldInfo field = type.GetField(name);

                DescriptionAttribute attribute = System.Attribute.GetCustomAttribute(field, typeof(DescriptionAttribute)) as DescriptionAttribute;



                if (attribute == null && nameInstead == true) {

                    return name;

                }

                return attribute?.Description;

            } catch {

                return string.Empty;

            }

        }