Remote app session state will enable communication between the ASP.NET Core and ASP.NET app to retrieve the session state. This is enabled by exposing an endpoint on the ASP.NET app that can be queried to retrieve and set the session state.
The <xref:System.Web.SessionState.HttpSessionState> object must be serialized for remote app session state to be enabled. This is accomplished through implementation of the type `Microsoft.AspNetCore.SystemWebAdapters.SessionState.Serialization.ISessionSerializer`, of which a default binary writer implementation is provided. This is added by the following code:
First, follow the [remote app setup](xref:migration/inc/remote-app-setup) instructions to connect the ASP.NET Core and ASP.NET apps. Then, there are just a couple extra extension methods to call to enable remote app session state.
Configuration for ASP.NET Core involves calling `AddRemoteAppSession` and `AddJsonSessionSerializer` to register known session item types. The code should look similar to the following:
Session support requires additional work for the ASP.NET Core pipeline, and is not turned on by default. It can be configured on a per-route basis via ASP.NET Core metadata.
For example, session support requires either to annotate a controller:
Readonly session will retrieve the session state from the framework app without any sort of locking. This consists of a single `GET` request that will return a session state and can be closed immediately.
## Writeable
Writeable session state protocol starts with the same as the readonly, but differs in the following:
- Requires an additional `PUT` request to update the state
- The initial `GET` request must be kept open until the session is done; if closed, the session will not be able to be updated
