Add IServiceScope support

Src/SmtpServer/ISessionServiceProviderFactory.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Threading.Tasks;
+
+namespace SmtpServer
+{
+    /// <summary>
+    /// Allows customization of the IServiceProvider instance that is used in the session context.
+    /// </summary>
+    public interface ISessionServiceProviderFactory
+    {
+        /// <summary>
+        /// Creates an IServiceProvider instance for one session context.
+        /// </summary>
+        IServiceProvider CreateServiceProvider(IServiceProvider rootServiceProvider);
+    }
+}

Src/SmtpServer/Net/IEndpointListener.cs

@@ -11,7 +11,7 @@ namespace SmtpServer.Net
     public interface IEndpointListener : IDisposable
     {
         /// <summary>
-        /// Returns a securtable pipe to the endpoint.
+        /// Returns a securable pipe to the endpoint.
         /// </summary>
         /// <param name="context">The session context that the pipe is being created for.</param>
         /// <param name="cancellationToken">The cancellation token.</param>

Src/SmtpServer/SmtpServer.cs

@@ -35,6 +35,7 @@ public class SmtpServer
         readonly ISmtpServerOptions _options;
         readonly IServiceProvider _serviceProvider;
         readonly IEndpointListenerFactory _endpointListenerFactory;
+        readonly ISessionServiceProviderFactory _sessionServiceProviderFactory;
         readonly SmtpSessionManager _sessions;
         readonly CancellationTokenSource _shutdownTokenSource = new CancellationTokenSource();
         readonly TaskCompletionSource<bool> _shutdownTask = new TaskCompletionSource<bool>();
@@ -50,6 +51,7 @@ public SmtpServer(ISmtpServerOptions options, IServiceProvider serviceProvider)
             _serviceProvider = serviceProvider;
             _sessions = new SmtpSessionManager(this);
             _endpointListenerFactory = serviceProvider.GetServiceOrDefault(EndpointListenerFactory.Default);
+            _sessionServiceProviderFactory = serviceProvider.GetServiceOrDefault<ISessionServiceProviderFactory>(null);
         }
 
         /// <summary>
@@ -128,7 +130,8 @@ async Task ListenAsync(IEndpointDefinition endpointDefinition, CancellationToken
 
             while (cancellationTokenSource.Token.IsCancellationRequested == false)
             {
-                var sessionContext = new SmtpSessionContext(_serviceProvider, _options, endpointDefinition);
+                var spForCtx = _sessionServiceProviderFactory?.CreateServiceProvider(_serviceProvider);
+                var sessionContext = new SmtpSessionContext(spForCtx ?? _serviceProvider, _options, endpointDefinition);
 
                 try
                 {
@@ -144,7 +147,7 @@ async Task ListenAsync(IEndpointDefinition endpointDefinition, CancellationToken
 
                 if (sessionContext.Pipe != null)
                 {
-                    _sessions.Run(sessionContext, cancellationTokenSource.Token);
+                    _sessions.Run(sessionContext, cancellationTokenSource.Token, spForCtx);
                 }
             }
         }

Src/SmtpServer/SmtpSessionManager.cs

@@ -16,9 +16,9 @@ internal SmtpSessionManager(SmtpServer smtpServer)
             _smtpServer = smtpServer;
         }
 
-        internal void Run(SmtpSessionContext sessionContext, CancellationToken cancellationToken)
+        internal void Run(SmtpSessionContext sessionContext, CancellationToken cancellationToken, IServiceProvider sessionServiceProvider)
         {
-            var handle = new SmtpSessionHandle(new SmtpSession(sessionContext), sessionContext);
+            var handle = new SmtpSessionHandle(new SmtpSession(sessionContext), sessionContext, sessionServiceProvider);
             Add(handle);
 
             handle.CompletionTask = RunAsync(handle, cancellationToken).ContinueWith(task =>
@@ -27,7 +27,7 @@ internal void Run(SmtpSessionContext sessionContext, CancellationToken cancellat
             });
         }
 
-        async Task RunAsync(SmtpSessionHandle handle, CancellationToken cancellationToken)
+        private async Task RunAsync(SmtpSessionHandle handle, CancellationToken cancellationToken)
         {
             using var sessionTimeoutCancellationTokenSource = new CancellationTokenSource(handle.SessionContext.EndpointDefinition.SessionTimeout);
 
@@ -58,6 +58,15 @@ async Task RunAsync(SmtpSessionHandle handle, CancellationToken cancellationToke
                 await handle.SessionContext.Pipe.Input.CompleteAsync();
 
                 handle.SessionContext.Pipe.Dispose();
+
+                if (handle.SessionServiceProvider is IAsyncDisposable asyncDisposable)
+                {
+                    await asyncDisposable.DisposeAsync();
+                } 
+                else if (handle.SessionServiceProvider is IDisposable disposable)
+                {
+                    disposable.Dispose();
+                }
             }
         }
 
@@ -91,16 +100,19 @@ void Remove(SmtpSessionHandle handle)
 
         class SmtpSessionHandle
         {
-            public SmtpSessionHandle(SmtpSession session, SmtpSessionContext sessionContext)
+            public SmtpSessionHandle(SmtpSession session, SmtpSessionContext sessionContext, IServiceProvider sessionServiceProvider)
             {
                 Session = session;
                 SessionContext = sessionContext;
+                SessionServiceProvider = sessionServiceProvider;
             }
 
             public SmtpSession Session { get; }
 
             public SmtpSessionContext SessionContext { get; }
 
+            public IServiceProvider SessionServiceProvider { get; }
+
             public Task CompletionTask { get; set; }
         }
     }