C中的行动授权#

我正在为一个API审查一个示例应用程序中的一些代码,需要一些帮助来更好地理解 Action<T> 整个示例应用程序的委派我在代码中提出了几个问题如有任何帮助,我们将不胜感激

API在 Client.cs 类,当我从应用程序发出请求时,API将响应发送到 客户机.cs 已经实施。

/*****  Client.cs  *****/

public event Action<int, int, int> TickSize;

void tickSize(int tickerId, int field, int size)
{
    var tmp = TickSize;

    //What is the point of tmp, and why do we check if it is not null?

    if (tmp != null)
        //This invokes the Action? ie - fires the TickSize Action event?
        tmp(tickerId, field, size);
}

然后 UI.cs 类处理用户界面交互并将信息反馈回用户界面,以便用户可以看到返回的数据

/*****  UI.cs  *****/

//Delegate to handle reading messages
delegate void MessageHandlerDelegate(Message message);

protected Client client;

public appDialog(){
    InitializeComponent();
    client = new Client();
    .
    .
    //Subscribes the client_TickSize method to the client.TickSize action?
    client.TickSize += client_TickSize;
}

void client_TickSize(int tickerId, int field, int size){
    HandleMessage(new Message(ticketID, field, size));
}

public void HandleMessage(Message message){
    //So, this.InvokeRequired checks if there is another thread accessing the method?
    //Unclear as to what this does and its purpose
    //What is the purpose of the MessageHandlerDelegate callback
    // - some clarification on what is going on here would be helpful
    if (this.InvokeRequired)
        {
            MessageHandlerDelegate callback = new MessageHandlerDelegate(HandleMessage);
            this.Invoke(callback, new object[] { message });
        }
        else
        {
            UpdateUI(message);
        }

}

private void UpdateUI(Message message) { handle messages }