如何使用 Visual Studio - 生成的异步 WCF 调用? [英] How to use Visual Studio - generated async WCF calls?

问题描述

我的OperationContract:

public List<MessageDTO> GetMessages()
        {
            List<MessageDTO> messages = new List<MessageDTO>();
            foreach (Message m in _context.Messages.ToList())
            {
                messages.Add(new MessageDTO()
                {
                    MessageID = m.MessageID,
                    Content = m.Content,
                    Date = m.Date,
                    HasAttachments = m.HasAttachments,
                    MailingListID = (int)m.MailingListID,
                    SenderID = (int)m.SenderID,
                    Subject = m.Subject
                });
            }
            return messages;
        }

在服务参考配置中，我选中了生成异步操作"选项.如何使用生成的 GetMessagesAsync()?在网上我发现使用 AsyncCallback 的例子，但我不熟悉.有没有办法以某种友好的方式使用它，例如 .NET 4.5 中的 async 和 await 关键字?如果不是，我该怎么做才能异步调用该方法?

In Service Reference configuration I checked the option "Generate asynchronous operations". How do I use the generated GetMessagesAsync()? In the net I found examples that use AsyncCallback, however I'm not familiar with that. Is there a way to use it in some friendly way like async and await keywords in .NET 4.5? If not, what should I do to invoke the method asynchronously?

推荐答案

如果您选择生成异步操作"，您将获得旧"行为，您必须使用回调.

If you select 'Generate asynchrounous operations', you will get the 'old' behavior where you have to use callbacks.

如果要使用新的 async/await 语法，则必须选择生成基于任务的操作"(默认选中).

If you want to use the new async/await syntax, you will have to select 'Generate task-based operations' (which is selected by default).

当使用默认的 Wcf 模板时，这将生成以下代理代码:

When using the default Wcf template, this will generate the following proxy code:

  public System.Threading.Tasks.Task<string> GetDataAsync(int value) {
      return base.Channel.GetDataAsync(value);
  }

如您所见，不再有回调.而是返回一个 Task.

As you can see, there are no more callbacks. Instead a Task<T> is returned.

您可以通过以下方式使用此代理:

You can use this proxy in the following way:

public static async Task Foo()
{
    using (ServiceReference1.Service1Client client = new ServiceReference1.Service1Client())
    {
        Task<string> t = client.GetDataAsync(1);
        string result = await t;
    }
}

你应该用 async 标记调用方法，然后在调用你的服务方法时使用 await.

You should mark the calling method with async and then use await when calling your service method.

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