Expose ConnectionId on .NET Client

src/SignalR/clients/csharp/Client.Core/ref/Microsoft.AspNetCore.SignalR.Client.Core.netstandard2.0.cs

@@ -26,6 +26,7 @@ public partial class HubConnection
         public static readonly System.TimeSpan DefaultServerTimeout;
         public HubConnection(Microsoft.AspNetCore.SignalR.Client.IConnectionFactory connectionFactory, Microsoft.AspNetCore.SignalR.Protocol.IHubProtocol protocol, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory) { }
         public HubConnection(Microsoft.AspNetCore.SignalR.Client.IConnectionFactory connectionFactory, Microsoft.AspNetCore.SignalR.Protocol.IHubProtocol protocol, System.IServiceProvider serviceProvider, Microsoft.Extensions.Logging.ILoggerFactory loggerFactory) { }
+        public string ConnectionId { get { throw null; } }
         public System.TimeSpan HandshakeTimeout { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } [System.Runtime.CompilerServices.CompilerGeneratedAttribute]set { } }
         public System.TimeSpan KeepAliveInterval { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } [System.Runtime.CompilerServices.CompilerGeneratedAttribute]set { } }
         public System.TimeSpan ServerTimeout { [System.Runtime.CompilerServices.CompilerGeneratedAttribute]get { throw null; } [System.Runtime.CompilerServices.CompilerGeneratedAttribute]set { } }

src/SignalR/clients/csharp/Client.Core/src/HubConnection.cs

@@ -54,6 +54,7 @@ public partial class HubConnection
         private long _nextActivationSendPing;
         private bool _disposed;
         private bool _hasInherentKeepAlive;
+        private string _connectionId;
 
         private CancellationToken _uploadStreamToken;
 
@@ -116,6 +117,13 @@ public partial class HubConnection
         /// </summary>
         public TimeSpan HandshakeTimeout { get; set; } = DefaultHandshakeTimeout;
 
+        /// <summary>
+        /// Gets the connection's current Id. This value will be cleared when the connection is stopped and will have a new value every time the connection is (re)established.
+        /// This value will be null if the negotiation step is skipped via HttpConnectionOptions or if the WebSockets transport is explicitly specified because the
+        /// client skips negotiation in that case as well.
+        /// </summary>
+        public string ConnectionId => _connectionId;
+
         /// <summary>
         /// Indicates the state of the <see cref="HubConnection"/> to the server.
         /// </summary>
@@ -338,6 +346,7 @@ private async Task StartAsyncCore(CancellationToken cancellationToken)
 
                 // Start the connection
                 var connection = await _connectionFactory.ConnectAsync(_protocol.TransferFormat);
+                _connectionId = connection.ConnectionId;
                 var startingConnectionState = new ConnectionState(connection, this);
                 _hasInherentKeepAlive = connection.Features.Get<IConnectionInherentKeepAliveFeature>()?.HasInherentKeepAlive ?? false;
 
@@ -405,6 +414,8 @@ private async Task StopAsyncCore(bool disposing)
                     (_serviceProvider as IDisposable)?.Dispose();
                     _disposed = true;
                 }
+
+                _connectionId = null;
             }
             finally
             {

src/SignalR/clients/csharp/Client/test/FunctionalTests/HubConnectionTests.cs

@@ -155,6 +155,41 @@ public async Task CanStopAndStartConnection(string protocolName, HttpTransportTy
             }
         }
 
+        [Theory]
+        [MemberData(nameof(HubProtocolsAndTransportsAndHubPaths))]
+        [LogLevel(LogLevel.Trace)]
+        public async Task CanAccessConnectionIdFromHubConnection(string protocolName, HttpTransportType transportType, string path)
+        {
+            var protocol = HubProtocols[protocolName];
+            using (StartServer<Startup>(out var server))
+            {
+                var connection = CreateHubConnection(server.Url, path, transportType, protocol, LoggerFactory);
+                try
+                {
+                    Assert.Null(connection.ConnectionId);
+                    await connection.StartAsync().OrTimeout();
+                    var originalClientConnectionId = connection.ConnectionId;
+                    var connectionIdFromServer = await connection.InvokeAsync<string>(nameof(TestHub.GetCallerConnectionId)).OrTimeout();
+                    Assert.Equal(connection.ConnectionId, connectionIdFromServer);
+                    await connection.StopAsync().OrTimeout();
+                    Assert.Null(connection.ConnectionId);
+                    await connection.StartAsync().OrTimeout();
+                    connectionIdFromServer = await connection.InvokeAsync<string>(nameof(TestHub.GetCallerConnectionId)).OrTimeout();
+                    Assert.NotEqual(originalClientConnectionId, connectionIdFromServer);
+                    Assert.Equal(connection.ConnectionId, connectionIdFromServer);
+                }
+                catch (Exception ex)
+                {
+                    LoggerFactory.CreateLogger<HubConnectionTests>().LogError(ex, "{ExceptionType} from test", ex.GetType().FullName);
+                    throw;
+                }
+                finally
+                {
+                    await connection.DisposeAsync().OrTimeout();
+                }
+            }
+        }
+
         [Theory]
         [MemberData(nameof(HubProtocolsAndTransportsAndHubPaths))]
         [LogLevel(LogLevel.Trace)]

src/SignalR/clients/csharp/Client/test/FunctionalTests/Hubs.cs

@@ -36,6 +36,11 @@ public async Task CallHandlerThatDoesntExist()
             await Clients.Client(Context.ConnectionId).SendAsync("NoClientHandler");
         }
 
+        public string GetCallerConnectionId()
+        {
+            return Context.ConnectionId;
+        }
+
         public ChannelReader<string> StreamEcho(ChannelReader<string> source) => TestHubMethodsImpl.StreamEcho(source);
 
         public string GetUserIdentifier()
@@ -110,6 +115,11 @@ public async Task CallHandlerThatDoesntExist()
             await Clients.Client(Context.ConnectionId).NoClientHandler();
         }
 
+        public string GetCallerConnectionId()
+        {
+            return Context.ConnectionId;
+        }
+
         public ChannelReader<string> StreamEcho(ChannelReader<string> source) => TestHubMethodsImpl.StreamEcho(source);
     }
 
@@ -135,6 +145,11 @@ public async Task CallHandlerThatDoesntExist()
             await Clients.Client(Context.ConnectionId).NoClientHandler();
         }
 
+        public string GetCallerConnectionId()
+        {
+            return Context.ConnectionId;
+        }
+
         public ChannelReader<string> StreamEcho(ChannelReader<string> source) => TestHubMethodsImpl.StreamEcho(source);
     }