使用 SQL Server 将信号器用户映射到连接

Question

我读到了这个topic，关于将 SignalR 用户映射到连接。简而言之，该主题解释了四种映射方法，我想使用第四种方法（永久，外部存储）。该方法使用 SQL Server 数据库存储ConnectionId，当客户端连接时（当OnConnected 方法被触发时）和当客户端关闭浏览器时（当OnDisconnected 方法被触发时）它只是使ConnectionId无效。

这是数据库的代码：

public class UserContext : DbContext
{
    public DbSet<User> Users { get; set; }
    public DbSet<Connection> Connections { get; set; }
}

public class User
{
    [Key]
    public string UserName { get; set; }
    public ICollection<Connection> Connections { get; set; }
}

public class Connection
{
    public string ConnectionID { get; set; }
    public string UserAgent { get; set; }
    public bool Connected { get; set; }
}

这里是 hub 类中的代码：

[Authorize]
public class ChatHub : Hub
{
    public void SendChatMessage(string who, string message)
    {
        var name = Context.User.Identity.Name;
        using (var db = new UserContext())
        {
            var user = db.Users.Find(who);
            if (user == null)
            {
                Clients.Caller.showErrorMessage("Could not find that user.");
            }
            else
            {
                db.Entry(user)
                    .Collection(u => u.Connections)
                    .Query()
                    .Where(c => c.Connected == true)
                    .Load();

                if (user.Connections == null)
                {
                    Clients.Caller.showErrorMessage("The user is no longer connected.");
                }
                else
                {
                    foreach (var connection in user.Connections)
                    {
                        Clients.Client(connection.ConnectionID)
                            .addChatMessage(name + ": " + message);
                    }
                }
            }
        }
    }

    public override Task OnConnected()
    {
        var name = Context.User.Identity.Name;
        using (var db = new UserContext())
        {
            var user = db.Users
                .Include(u => u.Connections)
                .SingleOrDefault(u => u.UserName == name);

            if (user == null)
            {
                user = new User
                {
                    UserName = name,
                    Connections = new List<Connection>()
                };
                db.Users.Add(user);
            }

            user.Connections.Add(new Connection
            {
                ConnectionID = Context.ConnectionId,
                UserAgent = Context.Request.Headers["User-Agent"],
                Connected = true
            });
            db.SaveChanges();
        }
        return base.OnConnected();
    }

    public override Task OnDisconnected(bool stopCalled)
    {
        using (var db = new UserContext())
        {
            var connection = db.Connections.Find(Context.ConnectionId);
            connection.Connected = false;
            db.SaveChanges();
        }
        return base.OnDisconnected(stopCalled);
    }
}

我想增强这种方法，因为使用这种方法会创建许多根本不需要的 ConnectionId。此外，使用这种方法，连接表将随着时间的推移而扩大，而没有任何用处。

Answer 1

如何清理 connectionIds 而不是将 Connected 属性设置为 false？您的 OnDisconnnected() 方法可能看起来像这样：

public override Task OnDisconnected(bool stopCalled)
{
    using (var db = new UserContext())
    {
        var connection = db.Connections.Find(Context.ConnectionId);
        db.Connections.Remove(connection);
        db.SaveChanges();
    }
    return base.OnDisconnected(stopCalled);
}

这将阻止 Connections 表无限增长。然后，您可以完全删除 Connected 属性，并让 Connection 行的存在表明连接处于活动状态。

更新

另一种方法，如果您不想删除记录但重新使用数据库中已有的记录，可能如下所示：

public override Task OnConnected()
{
    var name = Context.User.Identity.Name;
    using (var db = new UserContext())
    {
        var user = db.Users
            .Include(u => u.Connections)
            .SingleOrDefault(u => u.UserName == name);

        if (user == null)
        {
            user = new User
            {
                UserName = name,
                Connections = new List<Connection>()
            };
            db.Users.Add(user);
        }

        var connection = user.Connections.Where(c => c.Connected == false && UserAgent == Context.Request.Headers["User-Agent"]).FirstOrDefault();
        if (connection == null) 
        {
             connection = new Connection();
             connection.UserAgent = Context.Request.Headers["User-Agent"];
             user.Connections.Add(connection);
        }

        connection.ConnectionID = Context.ConnectionId;
        connection.Connected = true;
        db.SaveChanges();
    }
    return base.OnConnected();
}

这是否符合您的想法？