When you're using Azure SignalR Service, some APIs and features of ASP.NET SignalR aren't supported:
The ability to pass arbitrary state between clients and the hub (often called HubState) isn't supported.
The PersistentConnection class isn't supported.
Forever Frame transport isn't supported.
Azure SignalR Service no longer replays messages sent to the client when the client is offline.
When you're using Azure SignalR Service, the traffic for one client connection is always routed (also called sticky) to one app server instance for the duration of the connection.
Support for ASP.NET SignalR is focused on compatibility, so not all new features from ASP.NET Core SignalR are supported. For example, MessagePack and Streaming are available only for ASP.NET Core SignalR applications.
You can configure Azure SignalR Service for different service modes: Classic, Default, and Serverless. The Serverless mode isn't supported for ASP.NET. The data-plane REST API is also not supported.