InvalidDataContractException Class

public  class Test
{
    static void Main()
    {
        try
        {
            Test t = new Test();
            t.Run();
        }

        // Catch the InvalidDataContractException here.
        catch(InvalidDataContractException iExc)
        {
            Console.WriteLine("You have an invalid data contract: ");
            Console.WriteLine(iExc.Message);
            Console.ReadLine();

        }
          catch (Exception exc)
        {
            Console.WriteLine(exc.Message);
            Console.WriteLine(exc.ToString() );
            Console.ReadLine();
        }
    }

    private void Run()
    {
        // Create a new WSHttpBinding and set the security mode to Message;
        WSHttpBinding b = new WSHttpBinding(SecurityMode.Message);

        // Create a ServiceHost instance, and add a metadata endpoint.
        Uri baseUri= new Uri("http://localhost:1008/");            
        ServiceHost sh = new ServiceHost(typeof(Calculator), baseUri);

        // Optional. Add a metadata endpoint. The method is defined below.
        AddMetadataEndpoint(ref sh);

        // Add an endpoint using the binding, and open the service.
        sh.AddServiceEndpoint(typeof(ICalculator), b, "myCalculator");
        sh.Open();

        Console.WriteLine("Listening...");
        Console.ReadLine();

    }

    private void AddMetadataEndpoint(ref ServiceHost sh)
    {
        Uri mex = new Uri(@"http://localhost:1001/metadata/");
        ServiceMetadataBehavior sm = new ServiceMetadataBehavior();
        sm.HttpGetEnabled = true;
        sm.HttpGetUrl = mex;
        sh.Description.Behaviors.Add(sm);
    }

}

// This class will cause an InvalidDataContractException to be thrown because
// neither the DataContractAttribute nor DataMemberAttribute has been applied to it.
public class ExtraData
{
    public System.Collections.Generic.List<string> RandomData;
}

[ServiceContract(ProtectionLevel=System.Net.Security.ProtectionLevel.EncryptAndSign) ]
interface ICalculator
{
    [OperationContract]
    double Add(double a, double b);

    [OperationContract]
    ExtraData MoreData();
}

public class Calculator : ICalculator
{ 
    public double Add(double a, double b)
    {
        return a + b;
    }

    public ExtraData MoreData()
    {
        ExtraData ex = new ExtraData();
        ex.RandomData.Add("Hello");
        ex.RandomData.Add( "World" );
        return ex;
    }
}