Modified the initialization process a little to better control when a context is marked as initialized.

NSspi/Contexts/ClientContext.cs

@@ -114,15 +114,11 @@ namespace NSspi.Contexts
 
             if ( status == SecurityStatus.OK )
             {
-                this.Initialized = true;
+                base.Initialize( rawExpiry.ToDateTime() );
                 outToken = null;
-
-                this.Expiry = rawExpiry.ToDateTime();
             }
             else if ( status == SecurityStatus.ContinueNeeded )
             {
-                this.Initialized = false;
-
                 outToken = new byte[outTokenBuffer.Length];
                 Array.Copy( outTokenBuffer.Buffer, outToken, outToken.Length );
             }

NSspi/Contexts/Context.cs

@@ -26,11 +26,11 @@ namespace NSspi.Contexts
         /// <summary>
         /// Whether or not the context is fully formed.
         /// </summary>
-        public bool Initialized { get; protected set; }
+        public bool Initialized { get; private set; }
 
         protected Credential Credential { get; private set; }
 
-        public SafeContextHandle ContextHandle { get; protected set; }
+        public SafeContextHandle ContextHandle { get; private set; }
 
         public string AuthorityName
         {
@@ -48,10 +48,20 @@ namespace NSspi.Contexts
             }
         }
 
-        public DateTime Expiry { get; protected set; }
+        public DateTime Expiry { get; private set; }
 
         public bool Disposed { get; private set; }
 
+        /// <summary>
+        /// Marks the context as having completed the initialization process, ie, exchanging of authentication tokens.
+        /// </summary>
+        /// <param name="expiry">The date and time that the context will expire.</param>
+        protected void Initialize( DateTime expiry )
+        {
+            this.Expiry = expiry;
+            this.Initialized = true;
+        }
+
         public void Dispose()
         {
             Dispose( true );

NSspi/Contexts/ServerContext.cs

@@ -36,8 +36,8 @@ namespace NSspi.Contexts
 
         public SecurityStatus AcceptToken( byte[] clientToken, out byte[] nextToken )
         {
-            SecureBuffer clientBuffer = new SecureBuffer( clientToken, BufferType.Token );
-            SecureBuffer outBuffer = new SecureBuffer( new byte[12288], BufferType.Token );
+            SecureBuffer clientBuffer;
+            SecureBuffer outBuffer;
 
             SecurityStatus status;
             TimeStamp rawExpiry = new TimeStamp();
@@ -49,6 +49,15 @@ namespace NSspi.Contexts
             {
                 throw new ObjectDisposedException( "ServerContext" );
             }
+            else if( this.Initialized )
+            {
+                throw new InvalidOperationException( 
+                    "Attempted to continue initialization of a ServerContext after initialization had completed."
+                );
+            }
+
+            clientBuffer = new SecureBuffer( clientToken, BufferType.Token );
+            outBuffer = new SecureBuffer( new byte[12288], BufferType.Token );
 
             using ( clientAdapter = new SecureBufferAdapter( clientBuffer ) )
             {
@@ -90,7 +99,8 @@ namespace NSspi.Contexts
             if ( status == SecurityStatus.OK )
             {
                 nextToken = null;
-                this.Initialized = true;
+
+                base.Initialize( rawExpiry.ToDateTime() );
 
                 if ( outBuffer.Length != 0 )
                 {
@@ -101,13 +111,9 @@ namespace NSspi.Contexts
                 {
                     nextToken = null;
                 }
-
-                this.Expiry = rawExpiry.ToDateTime();
             }
             else if ( status == SecurityStatus.ContinueNeeded )
             {
-                this.Initialized = false;
-
                 nextToken = new byte[outBuffer.Length];
                 Array.Copy( outBuffer.Buffer, nextToken, nextToken.Length );
             }