Question

我有项目，Client类在哪里。我想要创建一个客户端对象的事件。我阅读有关事件的信息，但我仍然在雾中如何使用事件这是我的代码：

public class Client
{
    public string FirstName { get; set; }
    public string SecondName { get; set; }
    public string DateOfBirth { get; set; }
    public string Address { get; set; }

    public Client(string name, string surname, string dateOfBirth, string address)
    {
        FirstName = name;
        SecondName = surname;
        DateOfBirth = name;
        Address = address;
    }

    public event EventHandler NewClient;

    public virtual void OnNewClient(object sender, EventArgs e)
    {
        NewClient(this, e);
    }

class Program
{
    static void Main(string[] args)
    {
        Client client = new Client();
        client.OnNewClient();

    }


    public void CreateNewClient( string name, string surname, string dateOfBirth, string address)
    {
        string Name = name;
        string Surname = surname;
        string Date = dateOfBirth;
        string Address = address;

        Client client = new Client(Name, Surname,Date, Address);
    }
}

Answer 1

我不知道应该从哪里开始......事件属于一个对象，需要订阅。因此，在您创建的对象上创建事件并不是很有用，因为您必须在实际创建对象之前订阅事件（这是不可能的）。相反，事件应该在那里，CreateNewClient方法存在。说到这一点，您可能希望它也返回创建的客户端。那种方法应该引发事件。

正确的解决方案可能看起来像这样：

// Client class only cares about itself; is completely independent public class Client { public string FirstName { get; set; } public string SecondName { get; set; } public string DateOfBirth { get; set; } public string Address { get; set; } public Client(string name, string surname, string dateOfBirth, string address) { FirstName = name; SecondName = surname; DateOfBirth = name; Address = address; } } // Client factory is responsible for creating clients class ClientFactory { // Event name should describe what happened public event EventHandler ClientCreated; public Client CreateNewClient(string name, string surname, string dateOfBirth, string address) { // no need to copy the arguments into new local variables again; arguments // are already local Client client = new Client(name, surname, dateOfBirth, address); // raise the ClientCreated event OnClientCreated(); // return the created client return client; } // provide this proctected virtual method for raising the event protected virtual void OnClientCreated(EventArgs e) { var handler = ClientCreated; if (handler != null) handler(this, e); } // provide private specialized versions for convenience (e.g. to call it without // passing an argument) private void OnClientCreated() { OnClientCreated(EventArgs.Empty); } }

像这样使用：

// create the client factory ClientFactory factory = new ClientFactory(); // subscribe to the event factory.ClientCreated += (s, e) => { Console.WriteLine("Client created."); }; // create clients Client c1 = factory.CreateNewClient("Foo", "Bar", "Baz", "Baf"); Client c2 = factory.CreateNewClient("Foo", "Bar", "Baz", "Baf");

Answer 2

使用此代码，该事件几乎永远不会工作;因为该对象不存在，并且在创建后立即引发该事件。

换句话说：没有人有机会注册该活动！

如果确实想要这种行为，请考虑使用工厂：

public static class ClientFactory
{
     public static event Action ClientCreated;
     public static Client CreateClient(..)
     {
         Client retValue = new Client(...);

         if (ClientCreated != null)
             ClientCreated();

         return retValue;
     }
}

现在您有一个客户端对象可以注册的持久性事件。请注意，static不是最佳方式来实现它;它只是打字最快的。随意使用更好的Factory模式实现。

使用事件创建对象

2 个答案: