Check for null hub name

src/Microsoft.Azure.SignalR.Management/DependencyInjectionExtensions.cs

@@ -52,6 +52,15 @@ public static IServiceCollection AddSignalRServiceManager<TOptionsSetup>(this IS
     public static IServiceCollection AddHub<THub>(this IServiceCollection services, string hubName)
         where THub : Hub
     {
+#if NET6_0_OR_GREATER
+        ArgumentNullException.ThrowIfNull(hubName);
+#else
+        if (hubName is null)
+        {
+            throw new ArgumentNullException(nameof(hubName));
+        }
+#endif
+
         //for persistent 
         //use TryAdd to avoid overriding the test implementation added before.
         services.TryAddSingleton<IServiceConnectionContainer>(sp => sp.GetRequiredService<MultiEndpointConnectionContainerFactory>().Create(hubName));

src/Microsoft.Azure.SignalR.Management/ServiceHubContextBuilder.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft. All rights reserved.
+// Copyright (c) Microsoft. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System;
@@ -64,12 +64,15 @@ private async Task<IHost> CreateAndStartHost(CancellationToken cancellationToken
             }
             catch
             {
-                using (host)
+                if (host is not null)
                 {
-                    await host.StopAsync(CancellationToken.None);
+                    using (host)
+                    {
+                        await host.StopAsync(CancellationToken.None);
+                    }
                 }
                 throw;
             }
         }
     }
-}
+}

test/Microsoft.Azure.SignalR.Management.Tests/DependencyInjectionExtensionFacts.cs

@@ -438,6 +438,13 @@ public async Task HttpClientMessageTracingIdDisabledTestAsync(string httpClientN
         await httpClient.SendAsync(new HttpRequestMessage(HttpMethod.Get, "http://abc"));
     }
 
+    [Fact]
+    public void AddHub_HubNameNull_Throw()
+    {
+        Assert.Throws<ArgumentNullException>(
+            () => new ServiceCollection().AddHub<Hub>(null));
+    }
+
     private sealed class WaitInfinitelyHandler : DelegatingHandler
     {
         protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)