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 {
     MyServiceClient client;
     
     public Program() {
        client = new MyServiceClient(new NetTcpBinding(), new EndpointAddress("net.tcp://localhost:8523"));
     } 
     async Task<DataTable> tGetTable() {
         this.Info=Info;
         Task<DataTable> tdt = new Task<DataTable>(mtd_Запрос);
         tdt.Start();
         await tdt;
         return tdt.Result;
      }
    DataTable mtd_Запрос(){ return client.GetTable();}

    static void Main(string[] args) {
       Program oPrg = new Program();
       Task<byte[]> tdt = oPrg.tGetTable();
       //tdt.Wait();
       while (!xtb.IsCompleted ) {
          //-- Делаем что-нибудь видимое, двигаем ProgressBar к примеру
          . . .
          Thread.Sleep(500);
       }

       DataTable table = tdt.Result;
       foreach (DataRow row in table.Rows)
       Console.WriteLine(row["surname"]);
    }

      Console.ReadKey();
    }
  }
}

 
       var table = await oPrg.tGetTable();

       foreach (DataRow row in table.Rows)
       Console.WriteLine(row["surname"]);