Make McpSession field private

Author: halter73

src/ModelContextProtocol/Server/McpServer.cs

@@ -72,7 +72,7 @@ private McpServer(McpServerOptions options, ILoggerFactory? loggerFactory, IServ
 
         _toolsChangedDelegate = delegate
         {
-            _ = _session?.SendMessageAsync(new JsonRpcNotification()
+            _ = SendMessageAsync(new JsonRpcNotification()
             {
                 Method = NotificationMethods.ToolListChangedNotification,
             });
@@ -141,9 +141,6 @@ public async Task AcceptSessionAsync(CancellationToken cancellationToken = defau
     /// <inheritdoc />
     public async Task RunAsync(CancellationToken cancellationToken = default)
     {
-        // Below is effectively an assertion. The McpServerFactory should not return before the _transport is initialized.
-        Throw.IfNull(_session);
-
         try
         {
             // Start processing messages

src/ModelContextProtocol/Shared/McpJsonRpcEndpoint.cs

@@ -19,12 +19,12 @@ internal abstract class McpJsonRpcEndpoint : IAsyncDisposable
     private readonly RequestHandlers _requestHandlers = [];
     private readonly NotificationHandlers _notificationHandlers = [];
 
+    private McpSession? _session;
     private CancellationTokenSource? _sessionCts;
     private int _started;
     private int _disposed;
 
     protected readonly ILogger _logger;
-    protected McpSession? _session;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="McpJsonRpcEndpoint"/> class.