如何使用 SignalR 在 ASP .NET Core Web Api 中获取用户 2 连接 ID

Question

我想要用户 1 向用户 2 发送消息，但要做到这一点，我必须获取用户 2 连接 ID

因此，当我每次尝试发送消息时，它都会获取用户 1 连接 ID 并将其添加到此代码中

public async Task SendMessage(string targetConnectionId, string message)
{
    //await Clients.All.SendAsync("ReceiveMessage", targetConnectionId, message);

    await Clients.User(user).SendAsync("ReceiveMessage", targetConnectionId, message); 
}

那么我怎样才能获取用户2的连接ID，这样我就可以从用户1向用户2发送消息给他

Answer 1

测试结果

测试代码

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Connections.Features;
using Microsoft.AspNetCore.SignalR;
using System.Collections.Concurrent;
using System.Diagnostics;

namespace SignalRMiddleawre.Hubs
{

    [Authorize]
    public partial class MainHub : Hub
    {
        #region Connection
        /// <summary>
        /// Use ConcurrentDictionary to save connected users's id and connectionId
        /// </summary>
        private static ConcurrentDictionary<string, List<string>>? ConnectedUsers = new ConcurrentDictionary<string, List<string>>();

        /// <summary>
        ///  OnConnectedAsync method
        /// </summary>
        /// <param name="userid"></param>
        /// <returns></returns>
        /// 
        public override async Task OnConnectedAsync()
        {

            string? userid = Context.User?.Identity?.Name;
            if (userid == null || userid.Equals(string.Empty))
            {
                Trace.TraceInformation("user not loged in, can't connect signalr service");
                return;
            }
            Trace.TraceInformation(userid + "connected");
            // save connection
            List<string>? existUserConnectionIds = null;
            ConnectedUsers?.TryGetValue(userid, out existUserConnectionIds);
            if (existUserConnectionIds == null)
            {
                existUserConnectionIds = new List<string>();
            }
            existUserConnectionIds.Add(Context.ConnectionId);
            ConnectedUsers?.TryAdd(userid, existUserConnectionIds);
            await base.OnConnectedAsync();
        }

        /// <summary>
        /// OnDisconnectedAsync
        /// </summary>
        /// <param name="userid"></param>
        /// <returns></returns>
        public override async Task OnDisconnectedAsync(Exception? exception)
        {
            string? userid = Context.User?.Identity?.Name;
            // save connection
            List<string>? existUserConnectionIds= new List<string>() ;

            ConnectedUsers?.TryGetValue(userid, out existUserConnectionIds);

            existUserConnectionIds?.Remove(Context.ConnectionId);

            if (existUserConnectionIds?.Count == 0)
            {
                List<string> garbage;
                ConnectedUsers?.TryRemove(userid, out garbage);
            }

            await base.OnDisconnectedAsync(exception);
        }
        #endregion

        #region Message
        
        public async Task SendToSingleUser(string userid, string message)
        {
            List<string>? existUserConnectionIds = null;

            ConnectedUsers?.TryGetValue(userid, out existUserConnectionIds);

            if (existUserConnectionIds == null)
            {
                existUserConnectionIds = new List<string>();
            }
            existUserConnectionIds.Add(Context.ConnectionId);
            ConnectedUsers?.TryAdd(userid, existUserConnectionIds);

            string? fromUser = Context.User?.Identity?.Name;
            string? ToUser = userid;
            await Clients.Clients(existUserConnectionIds).SendAsync("ReceiveMessage_SpecificUser", fromUser,ToUser, message);
        }
        #endregion

    }
}