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Microsoft.AspNetCore.SignalR.Client

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public class ChatHub:Hub
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{
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    private static int _connectionCount;
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    public async Task SendComment(string content)
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    {
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    ZyComments comment = new ZyComments
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        {
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            Content = content
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        };
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        //广播评论给所有连接的客户端
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    await Clients.All.SendAsync("ReceiveComment", comment);
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    }
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    public override Task OnConnectedAsync()
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    {
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      // 每次客户端连接时增加计数
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        Interlocked.Increment(ref _connectionCount);
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        return base.OnConnectedAsync();
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    }
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    public override Task OnDisconnectedAsync(Exception? exception)
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    {
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      // 每次客户端断开连接时减少计数
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        Interlocked.Decrement(ref _connectionCount);
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        // 广播连接数量变化
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    _ = BroadcastConnectionCount();
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        return base.OnDisconnectedAsync(exception);
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    }
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    public int GetConnectionCount()
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    {
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    // 获取当前连接数量
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        return _connectionCount;
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    }
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    public async Task BroadcastConnectionCount()
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    {
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      await Clients.All.SendAsync("ConnectionCountChanged", _connectionCount);
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    }
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}

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builder.Services.AddSignalR();
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app.MapHub<ChatHub>("/ChatHub");

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import * as signalR from '@microsoft/signalr';
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const connectionCount = ref(0);// 连接数量
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let connection: signalR.HubConnection | null = null;
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connection = new signalR.HubConnectionBuilder()
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    .withUrl('https://localhost:44323/ChatHub') //后端地址
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    .build();
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//订阅评论消息事件
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connection.on('ReceiveComment', (comment: any) => {
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  comments.value.push(comment);
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  const _danmuMsg =
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      {
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        ...
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      }
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  danmaku.value.add(_danmuMsg)
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});
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// 订阅连接数量变化事件
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connection.on('ConnectionCountChanged', (count) => {
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  connectionCount.value = count;
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  console.log(`当前连接数量：${count}`);
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});
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//连接成功后调用BroadcastConnectionCount方法广播一次
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connection.start().then(()=>{
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  connection.invoke('BroadcastConnectionCount')
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      .catch(err => console.error(err.toString()));
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}).catch(err => console.error(err.toString()));
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......