[ServiceContract(Name="CalculatorService", Namespace="http://service.com")]
  public interface ICalculator
  {
        [OperationContract]
        double Add(double x, double y,out int oi);
  }
  public class CalculatorService:ICalculator
  {
     public double Add(double x, double y,out int oi)
     {
         oi=1;
         return x + y;
     }
  }

------解决方案--------------------

应该是支持的，求出错的项目示例，模拟下错误的现象才能诊断这种怪异现象。