对象引用未设置为实例-事件和委托

问题描述

嗨

我有两个名为ChatServer和ChatClient的项目.当用户单击登录按钮时，我利用事件和委托来引发事件.

ChatServer上的代码是:

Hi

I have two projects named ChatServer and ChatClient. I make use of events and delegats to raise the event when user clicks on login button.

The code on ChatServer is:

public class ChatServerClass : IServiceInterface
   {
       public delegate void UserJoin(string username);

       public event UserJoin Newjoin;
       public void JoinChat(string name)
       {

           if (flag == true)
           {
              ListofUsers.Add(name);
              MessageBox.Show("User Logged in");
              Newjoin(name);
           }
           else
               MessageBox.Show("Select other Name");

           ListofUsers.ToArray();

       }

ChatClient上的代码是

The code on ChatClient is

private void login_btn_Click(object sender, EventArgs e)
{
//Client newclient = new Client(login_txt.Text);
username = login_txt.Text;
//InstanceContext context = new InstanceContext(Icall);
//connect.Open();
client.JoinChat(username);
ChatServerClass cs=new ChatServerClass();
cs.Newjoin+=new Userjoin(UserEnter);

 public void UserEnter(string username)
{
MessageBox.Show("User" +username + "is online");

}

在ChatServer中添加了对ChatClient的引用.我的意思是我在ChatServer项目中使用ChatClient参考添加.当我单击登录按钮时，出现异常，提示未将tat对象引用设置为实例.

请帮助

The reference to ChatClient is added in ChatServer. I mean i am adding using ChatClient reference in ChatServer project. When i click on the login button i get exception saying tat object reference not set to the instance.

PLease help

推荐答案

if (flag == true)
{
    ListofUsers.Add(name);
    MessageBox.Show("User Logged in");

    UserJoin handler = Newjoin; // this is not necesarry, it just
    if(handler != null)         // to make it threadsafe.
        handler (name);
}

client.JoinChat(username);

实例化了客户端对象吗?究竟是什么对象?

干杯...

have you instantiated the client object?? what object exactly its meant to be?

Cheers...

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