如何在 C# 中生成从库到应用程序的回调（事件）

Question

我正在开发一个库 (DLL)，我需要在其中向用户提供事件（中断）作为一种数据方法。图书馆的工作是开始在套接字上列出，从套接字接收数据并以一种方法将这些数据传递给用户。

图书馆：

public void start(string IP, int port)
{
    // start logic...

    // receives data from socket... send this data to user

}

应用：

Library. Class a = new Library. Class();
a.start(ip, port);

// I need this method called by library automatically when it receives data...

void receivedData(string data)
{
    // data which received by library....
}

如何使用库中的数据向应用程序发起事件？

提前谢谢....

Answer 1

您应该更改 start 方法的签名以传递委托：

public void start(string IP, int port, Action<string> callback)
{
    // start logic...

    // receives data from socket... send this data to user
    callback(data);
}

Library. Class a = new Library. Class();
a.start(ip, port, receivedData);

// I need this method called by library automatically when it receives data...

void receivedData(string data)
{
    // data which received by library....
}

Answer 2

像这样将事件添加到您的库中：

public event Action<string> OnDataReceived = null;

然后，在应用程序中：

Library.Class a = new Library.Class();
a.OnDataReceived += receivedData;
a.start(ip, port);

就是这样。

但是你可能想用约定来编写事件，我建议你开始习惯它，因为 .NET 就是这样使用事件的，所以每当你遇到那个约定时，你就会知道它是事件。 因此，如果我稍微重构您的代码，它应该是这样的：

在你的类库中：

//...
public class YourEventArgs : EventArgs
{
   public string Data { get; set; }
}
//...

public event EventHandler DataReceived = null;
...
protected override OnDataReceived(object sender, YourEventArgs e)
{
   if(DataReceived != null)
   {
      DataReceived(this, new YourEventArgs { Data = "data to pass" });
   }
}

当您的类库想要启动事件时，它应该调用 OnDataReceived，它负责检查是否有人在监听并构造适当的 EventArgs 以将您的数据传递给监听器。

在应用程序中你应该改变你的方法签名：

Library.Class a = new Library.Class();
a.DataReceived += ReceivedData;
a.start(ip, port);

//...

void ReceivedData(object sender, YourEventArgs e)
{
  string data = e.Data;
  //...
}

Answer 3

为您的班级添加活动

public event DataReceivedEventHandler DataReceived;
public delegate void DataReceivedEventHandler(object sender, SocketDataReceivedEventArgs e);

创建一个包含所需参数的类，例如 Ex : SocketDataReceivedEventArgs here

触发事件，如

SocketDataReceivedEventArgs DataReceiveDetails = new SocketDataReceivedEventArgs();
DataReceiveDetails.data = "your data here";
DataReceived(this, DataReceiveDetails);

在应用程序创建方法中

void receivedData(object sender, SocketDataReceivedEventArgs e)
{
    // e.data is data which received by library....
}

现在将处理程序附加到它

 Library. Class a = new Library. Class();
    a.DataReceived += receivedData;
    a.start(ip, port);

您需要根据您的要求在多个线程中编写它 以下是如何在上面添加线程安全支持

Dispatcher.Invoke and accessing textbox from another thread