/// <summary>
        /// Initialises a new instance of <see cref="ExportServiceAttribute" />.
        /// </summary>
        /// <param name="name">The name of the service.</param>
        /// <param name="serviceType">The service type.</param>
        public ExportServiceAttribute(string name, string description, Type serviceType,
                                      Type contactType, int order = 1, TokenValidationMode mode = TokenValidationMode.Check)
            : base(typeof(IHostedService))
        {
            if (string.IsNullOrWhiteSpace(name))
            {
                throw new ArgumentException("Name is a required parameter.", "name");
            }

            if (serviceType == null)
            {
                throw new ArgumentNullException("serviceType");
            }

            if (order < 0)
            {
                throw new ArgumentException("Order is must great than zero.", "order");
            }

            Name                = name;
            Description         = description;
            ServiceType         = serviceType;
            ContactType         = contactType;
            Order               = order;
            TokenValidationMode = mode;
        }
        /// <summary>
        /// Initialises a new instance of <see cref="ExportServiceAttribute" />.
        /// </summary>
        /// <param name="name">The name of the service.</param>
        /// <param name="serviceType">The service type.</param>
        public ExportServiceAttribute(string name, string description, Type serviceType, 
            Type contactType, int order = 1, TokenValidationMode mode = TokenValidationMode.Check)
            : base(typeof(IHostedService))
        {
            if (string.IsNullOrWhiteSpace(name))
                throw new ArgumentException("Name is a required parameter.", "name");

            if (serviceType == null)
                throw new ArgumentNullException("serviceType");

            if (order < 0)
                throw new ArgumentException("Order is must great than zero.", "order");

            Name = name;
            Description = description;
            ServiceType = serviceType;
            ContactType = contactType;
            Order = order;
            TokenValidationMode = mode;
        }