WCF unable to access a class file even after decorating it with data contract attribute

See more:

WCFServices

[KnownType(typeof(FullTimeEmployee))]
    [KnownType(typeof(PartTimeEmployee))]

    [DataContract(Name = "http://CodeAce.com/EmployeeApp")]
    public class Employee
    {

        private int _id;
        private string _name;
        private string _gender;
        private DateTime _dateOfBirth;

        [DataMember(Name = "ghgh", Order = 1)]
        public int Id
        {
            get { return _id; }
            set { _id = value; }
        }

        [DataMember(Name = "grrrr", Order = 2)]
        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }

        [DataMember(Name = "gssss", Order = 3)]

        public string Gender
        {
            get { return _gender; }
            set { _gender = value; }
        }

        [DataMember(Name = "gkkkkk", Order = 4)]

        public DateTime DateOfBirth
        {
            get { return _dateOfBirth; }
            set { _dateOfBirth = value; }
        }
        [DataMember(Name = "gbbbb", Order = 5)]
        public EmployeeType Type { get; set; }
    }
    public enum EmployeeType
    {
        FullTimeEmployee = 1,
        PartTimeEmployee = 2
    }

}

I wrote this class as part of class library project and added a wcf service to the project.when i try to create an object of this class in the web app where i try to consume the service it shows an error "employee does not exist in the current context missing an assembly refernce".The classes that are derived from this class are accessible though.Can any one please help me.