using System;
using System.Data;
using System.ServiceModel;

namespace ContractWCF
{
  [ServiceContract]
  public interface IMyContract
  {
    [OperationContract]
    DataTable GetTable();
  }
}

using ContractWCF;
using System;
using System.Data;
using System.Data.OleDb;
using System.ServiceModel;

namespace ServerWcf
{
  public class MyService : IMyContract
  {
    public DataTable GetTable()
    {
      OleDbConnection connection = new OleDbConnection(
        @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=DB.mdb;Persist Security Info=False");
      OleDbCommand command = new OleDbCommand("select * from People", connection);
      OleDbDataAdapter adapter = new OleDbDataAdapter(command);
      DataTable table = new DataTable("People");
      adapter.Fill(table);
      return table;
    }
  }

  class Program
  {
    static void Main(string[] args)
    {
      ServiceHost host = new ServiceHost(typeof(MyService), new Uri("net.tcp://localhost:8523"));
      host.AddServiceEndpoint(typeof(IMyContract), new NetTcpBinding(), "");
      host.Open();
      Console.WriteLine("Для завершения нажмите enter.");
      Console.ReadLine();
      host.Close();
    }
  }
}

using ContractWCF;
using System;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.Data;

namespace ClientWcf
{
  public class MyServiceClient : ClientBase<IMyContract>, IMyContract
  {
    public MyServiceClient(Binding binding, EndpointAddress endpointAddress) : base(binding, endpointAddress) { }

    public DataTable GetTable()
    {
      return Channel.GetTable();
    }
  }

  class Program
  {
    static void Main(string[] args)
    {
      using (MyServiceClient client = new MyServiceClient(new NetTcpBinding(), new EndpointAddress("net.tcp://localhost:8523")))
      {
        DataTable table = client.GetTable();
        foreach (DataRow row in table.Rows)
          Console.WriteLine(row["surname"]);
      }

      Console.ReadKey();
    }
  }
}