如何等待异步wcf调用完成才能使用结果

我需要进行两次wcf调用来构建模型

[SecurityOperationBehavior]
public Response1 Func1(Request1 req)
{
}

[SecurityOperationBehavior]
public Response2 Func2(Request2 req)
{
}

我知道我需要使用TaskCompletionSource来等待两个调用都完成。

public FullResult GetResult(int id)
{
  Request1 req = new Request1 ();
  req.id = id;
  Request2 req2 = new Request2 ();
  req2.id = id;
  var taskCompletions = new[]
                         {
                            new TaskCompletionSource<object>(),
                            new TaskCompletionSource<object>()
                           };
 var tasks = new[] { taskCompletions[0].Task, taskCompletions[1].Task  };
  System.Threading.Tasks.Task.Factory.StartNew(()=>Func1(req );
  System.Threading.Tasks.Task.Factory.StartNew(()=>Func2(req2 );
  System.Threading.Tasks.Task.WaitAll(tasks);
   //the following is what I want to do. The results of the 
   //two service calls will be contained in the the full result
    FullResult  result = new FullResult();
   result.first = tasks[0].Result;
   result.second = tasks[0].Result;
   return Result;

}

问题：

两个服务调用完成后，我如何设置结果？

public FullResult GetResult(int id)
{
    Request1 req = new Request1();
    req.id = id;
    Request2 req2 = new Request2();
    req2.id = id;
    var tasks = new Task[] {
        Task.Factory.StartNew(() => Func1(req))
        , Task.Factory.StartNew(() => Func2(req2))};
    System.Threading.Tasks.Task.WaitAll(tasks);
    FullResult result = new FullResult();
    result.first = tasks[0];
    result.second = tasks[1];
    return result;
}