Example #1
0
        /// <summary>
        /// Starts connection to the specified host.
        /// </summary>
        /// <param name="host">Host name or IP address.</param>
        /// <param name="port">Port to connect.</param>
        /// <param name="ssl">Specifies if connects to SSL end point.</param>
        /// <param name="callback">Callback to call when the connect operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous connection.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when TCP client is already connected.</exception>
        /// <exception cref="ArgumentException">Is raised when any of the arguments has invalid value.</exception>
        public IAsyncResult BeginConnect(string host, int port, bool ssl, AsyncCallback callback, object state)
        {
            if (m_IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (IsConnected)
            {
                throw new InvalidOperationException("TCP client is already connected.");
            }
            if (string.IsNullOrEmpty(host))
            {
                throw new ArgumentException("Argument 'host' value may not be null or empty.");
            }
            if (port < 1)
            {
                throw new ArgumentException("Argument 'port' value must be >= 1.");
            }

            BeginConnectHostDelegate asyncMethod = Connect;
            AsyncResultState         asyncState  = new AsyncResultState(this, asyncMethod, callback, state);

            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(host,
                                                              port,
                                                              ssl,
                                                              asyncState.CompletedCallback,
                                                              null));

            return(asyncState);
        }
Example #2
0
        /// <summary>
        /// Starts authentication.
        /// </summary>
        /// <param name="userName">User login name.</param>
        /// <param name="password">Password.</param>
        /// <param name="tryApop"> If true and POP3 server supports APOP, then APOP is used, otherwise normal login used.</param>
        /// <param name="callback">Callback to call when the asynchronous operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous operation.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when POP3 client is not connected or is already authenticated.</exception>
        public IAsyncResult BeginAuthenticate(string userName,
                                              string password,
                                              bool tryApop,
                                              AsyncCallback callback,
                                              object state)
        {
            if (IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (!IsConnected)
            {
                throw new InvalidOperationException("You must connect first.");
            }
            if (IsAuthenticated)
            {
                throw new InvalidOperationException("Session is already authenticated.");
            }

            AuthenticateDelegate asyncMethod = Authenticate;
            AsyncResultState     asyncState  = new AsyncResultState(this, asyncMethod, callback, state);

            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(userName,
                                                              password,
                                                              tryApop,
                                                              asyncState.CompletedCallback,
                                                              null));

            return(asyncState);
        }
Example #3
0
        /// <summary>
        /// Starts connection to the specified remote end point.
        /// </summary>
        /// <param name="localEP">Local IP end point to use for connect.</param>
        /// <param name="remoteEP">Remote IP end point where to connect.</param>
        /// <param name="ssl">Specifies if connects to SSL end point.</param>
        /// <param name="callback">Callback to call when the connect operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous connection.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when TCP client is already connected.</exception>
        /// <exception cref="ArgumentNullException">Is raised when <b>remoteEP</b> is null.</exception>
        /// <exception cref="ArgumentException">Is raised when any of the arguments has invalid value.</exception>
        public IAsyncResult BeginConnect(IPEndPoint localEP,
                                         IPEndPoint remoteEP,
                                         bool ssl,
                                         AsyncCallback callback,
                                         object state)
        {
            if (m_IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (IsConnected)
            {
                throw new InvalidOperationException("TCP client is already connected.");
            }
            if (remoteEP == null)
            {
                throw new ArgumentNullException("remoteEP");
            }

            BeginConnectEPDelegate asyncMethod = Connect;
            AsyncResultState       asyncState  = new AsyncResultState(this, asyncMethod, callback, state);

            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(localEP,
                                                              remoteEP,
                                                              ssl,
                                                              asyncState.CompletedCallback,
                                                              null));

            return(asyncState);
        }
Example #4
0
        /// <summary>
        /// Ends a pending asynchronous disconnect request.
        /// </summary>
        /// <param name="asyncResult">An IAsyncResult that stores state information and any user defined data for this asynchronous operation.</param>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="ArgumentNullException">Is raised when <b>asyncResult</b> is null.</exception>
        /// <exception cref="ArgumentException">Is raised when argument <b>asyncResult</b> was not returned by a call to the <b>BeginDisconnect</b> method.</exception>
        /// <exception cref="InvalidOperationException">Is raised when <b>EndDisconnect</b> was previously called for the asynchronous connection.</exception>
        public void EndDisconnect(IAsyncResult asyncResult)
        {
            if (m_IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (asyncResult == null)
            {
                throw new ArgumentNullException("asyncResult");
            }

            AsyncResultState castedAsyncResult = asyncResult as AsyncResultState;

            if (castedAsyncResult == null || castedAsyncResult.AsyncObject != this)
            {
                throw new ArgumentException(
                          "Argument asyncResult was not returned by a call to the BeginDisconnect method.");
            }
            if (castedAsyncResult.IsEndCalled)
            {
                throw new InvalidOperationException(
                          "EndDisconnect was previously called for the asynchronous connection.");
            }

            castedAsyncResult.IsEndCalled = true;
            if (castedAsyncResult.AsyncDelegate is DisconnectDelegate)
            {
                ((DisconnectDelegate)castedAsyncResult.AsyncDelegate).EndInvoke(castedAsyncResult.AsyncResult);
            }
            else
            {
                throw new ArgumentException(
                          "Argument asyncResult was not returned by a call to the BeginDisconnect method.");
            }
        }
Example #5
0
        /// <summary>
        /// Starts switching to SSL.
        /// </summary>
        /// <returns>An IAsyncResult that references the asynchronous operation.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when POP3 client is not connected or is authenticated or is already secure connection.</exception>
        public IAsyncResult BeginStartTLS(AsyncCallback callback, object state)
        {
            if (IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (!IsConnected)
            {
                throw new InvalidOperationException("You must connect first.");
            }
            if (IsAuthenticated)
            {
                throw new InvalidOperationException(
                          "The STLS command is only valid in non-authenticated state.");
            }
            if (IsSecureConnection)
            {
                throw new InvalidOperationException("Connection is already secure.");
            }

            StartTLSDelegate asyncMethod = StartTLS;
            AsyncResultState asyncState  = new AsyncResultState(this, asyncMethod, callback, state);

            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(asyncState.CompletedCallback, null));

            return(asyncState);
        }
Example #6
0
        /// <summary>
        /// Starts disconnecting connection.
        /// </summary>
        /// <param name="callback">Callback to call when the asynchronous operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous disconnect.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when TCP client is not connected.</exception>
        public IAsyncResult BeginDisconnect(AsyncCallback callback, object state)
        {
            if (m_IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (!IsConnected)
            {
                throw new InvalidOperationException("TCP client is not connected.");
            }

            DisconnectDelegate asyncMethod = Disconnect;
            AsyncResultState   asyncState  = new AsyncResultState(this, asyncMethod, callback, state);

            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(asyncState.CompletedCallback, null));

            return(asyncState);
        }
Example #7
0
        /// <summary>
        /// Starts sending NOOP command to server. This method can be used for keeping connection alive(not timing out).
        /// </summary>
        /// <param name="callback">Callback to call when the asynchronous operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous operation.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when POP3 client is not connected.</exception>
        public IAsyncResult BeginNoop(AsyncCallback callback, object state)
        {
            if (IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (!IsConnected)
            {
                throw new InvalidOperationException("You must connect first.");
            }

            NoopDelegate     asyncMethod = Noop;
            AsyncResultState asyncState  = new AsyncResultState(this, asyncMethod, callback, state);

            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(asyncState.CompletedCallback, null));

            return(asyncState);
        }
Example #8
0
        /// <summary>
        /// Starts resetting session. Messages marked for deletion will be unmarked.
        /// </summary>
        /// <param name="callback">Callback to call when the asynchronous operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous operation.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when POP3 client is not connected and authenticated.</exception>
        public IAsyncResult BeginReset(AsyncCallback callback, object state)
        {
            if (IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (!IsConnected)
            {
                throw new InvalidOperationException("You must connect first.");
            }
            if (!IsAuthenticated)
            {
                throw new InvalidOperationException("The RSET command is only valid in authenticated state.");
            }

            ResetDelegate    asyncMethod = Reset;
            AsyncResultState asyncState  = new AsyncResultState(this, asyncMethod, callback, state);

            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(asyncState.CompletedCallback, null));

            return(asyncState);
        }
Example #9
0
        public IAsyncResult BeginReset(AsyncCallback callback,object state)
        {
            if(this.IsDisposed){
                throw new ObjectDisposedException(this.GetType().Name);
            }
            if(!this.IsConnected){
				throw new InvalidOperationException("You must connect first.");
			}

            ResetDelegate asyncMethod = new ResetDelegate(this.Reset);
            AsyncResultState asyncState = new AsyncResultState(this,asyncMethod,callback,state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(new AsyncCallback(asyncState.CompletedCallback),null));

            return asyncState;
        }
Example #10
0
        public IAsyncResult BeginRcptTo(string to,SMTP_DSN_Notify notify,string orcpt,AsyncCallback callback,object state)
        {
            if(this.IsDisposed){
                throw new ObjectDisposedException(this.GetType().Name);
            }
            if(!this.IsConnected){
				throw new InvalidOperationException("You must connect first.");
			}

            RcptToDelegate asyncMethod = new RcptToDelegate(this.RcptTo);
            AsyncResultState asyncState = new AsyncResultState(this,asyncMethod,callback,state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(to,notify,orcpt,new AsyncCallback(asyncState.CompletedCallback),null));

            return asyncState;
        }
Example #11
0
        public IAsyncResult BeginMailFrom(string from,long messageSize,SMTP_DSN_Ret ret,string envid,AsyncCallback callback,object state)
        {
            if(this.IsDisposed){
                throw new ObjectDisposedException(this.GetType().Name);
            }
            if(!this.IsConnected){
				throw new InvalidOperationException("You must connect first.");
			}

            MailFromDelegate asyncMethod = new MailFromDelegate(this.MailFrom);
            AsyncResultState asyncState = new AsyncResultState(this,asyncMethod,callback,state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(from,(int)messageSize,ret,envid,new AsyncCallback(asyncState.CompletedCallback),null));

            return asyncState;
        }
Example #12
0
        /// <summary>
        /// Starts switching to SSL.
        /// </summary>
        /// <returns>An IAsyncResult that references the asynchronous operation.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when SMTP client is not connected or is already secure connection.</exception>
        public IAsyncResult BeginStartTLS(AsyncCallback callback, object state)
        {
            if (IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (!IsConnected)
            {
                throw new InvalidOperationException("You must connect first.");
            }
            if (IsSecureConnection)
            {
                throw new InvalidOperationException("Connection is already secure.");
            }

            StartTLSDelegate asyncMethod = StartTLS;
            AsyncResultState asyncState = new AsyncResultState(this, asyncMethod, callback, state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(asyncState.CompletedCallback, null));

            return asyncState;
        }
Example #13
0
        public IAsyncResult BeginAuthenticate(string userName,string password,AsyncCallback callback,object state)
        {
            if(this.IsDisposed){
                throw new ObjectDisposedException(this.GetType().Name);
            }
            if(!this.IsConnected){
				throw new InvalidOperationException("You must connect first.");
			}
			if(this.IsAuthenticated){
				throw new InvalidOperationException("Session is already authenticated.");
			}

            AuthenticateDelegate asyncMethod = new AuthenticateDelegate(this.Authenticate);
            AsyncResultState asyncState = new AsyncResultState(this,asyncMethod,callback,state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(userName,password,new AsyncCallback(asyncState.CompletedCallback),null));

            return asyncState;
        }
Example #14
0
        /// <summary>
        /// Starts connection to the specified remote end point.
        /// </summary>
        /// <param name="localEP">Local IP end point to use for connect.</param>
        /// <param name="remoteEP">Remote IP end point where to connect.</param>
        /// <param name="ssl">Specifies if connects to SSL end point.</param>
        /// <param name="callback">Callback to call when the connect operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous connection.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when TCP client is already connected.</exception>
        /// <exception cref="ArgumentNullException">Is raised when <b>remoteEP</b> is null.</exception>
        /// <exception cref="ArgumentException">Is raised when any of the arguments has invalid value.</exception>
        public IAsyncResult BeginConnect(IPEndPoint localEP,
                                         IPEndPoint remoteEP,
                                         bool ssl,
                                         AsyncCallback callback,
                                         object state)
        {
            if (m_IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (IsConnected)
            {
                throw new InvalidOperationException("TCP client is already connected.");
            }
            if (remoteEP == null)
            {
                throw new ArgumentNullException("remoteEP");
            }

            BeginConnectEPDelegate asyncMethod = Connect;
            AsyncResultState asyncState = new AsyncResultState(this, asyncMethod, callback, state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(localEP,
                                                              remoteEP,
                                                              ssl,
                                                              asyncState.CompletedCallback,
                                                              null));

            return asyncState;
        }
Example #15
0
        /// <summary>
        /// Starts connection to the specified host.
        /// </summary>
        /// <param name="host">Host name or IP address.</param>
        /// <param name="port">Port to connect.</param>
        /// <param name="ssl">Specifies if connects to SSL end point.</param>
        /// <param name="callback">Callback to call when the connect operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous connection.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when TCP client is already connected.</exception>
        /// <exception cref="ArgumentException">Is raised when any of the arguments has invalid value.</exception>
        public IAsyncResult BeginConnect(string host, int port, bool ssl, AsyncCallback callback, object state)
        {
            if (m_IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (IsConnected)
            {
                throw new InvalidOperationException("TCP client is already connected.");
            }
            if (string.IsNullOrEmpty(host))
            {
                throw new ArgumentException("Argument 'host' value may not be null or empty.");
            }
            if (port < 1)
            {
                throw new ArgumentException("Argument 'port' value must be >= 1.");
            }

            BeginConnectHostDelegate asyncMethod = Connect;
            AsyncResultState asyncState = new AsyncResultState(this, asyncMethod, callback, state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(host,
                                                              port,
                                                              ssl,
                                                              asyncState.CompletedCallback,
                                                              null));

            return asyncState;
        }
Example #16
0
        /// <summary>
        /// Starts disconnecting connection.
        /// </summary>
        /// <param name="callback">Callback to call when the asynchronous operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous disconnect.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when TCP client is not connected.</exception>
        public IAsyncResult BeginDisconnect(AsyncCallback callback, object state)
        {
            if (m_IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (!IsConnected)
            {
                throw new InvalidOperationException("TCP client is not connected.");
            }

            DisconnectDelegate asyncMethod = Disconnect;
            AsyncResultState asyncState = new AsyncResultState(this, asyncMethod, callback, state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(asyncState.CompletedCallback, null));

            return asyncState;
        }
Example #17
0
        /// <summary>
        /// Starts sending RCPT TO: command to SMTP server.
        /// </summary>
        /// <param name="to">Recipient email address.</param>
        /// <param name="callback">Callback to call when the asynchronous operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous disconnect.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when SMTP client is not connected.</exception>
        public IAsyncResult BeginRcptTo(string to, AsyncCallback callback, object state)
        {
            if (IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (!IsConnected)
            {
                throw new InvalidOperationException("You must connect first.");
            }

            RcptToDelegate asyncMethod = RcptTo;
            AsyncResultState asyncState = new AsyncResultState(this, asyncMethod, callback, state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(to, asyncState.CompletedCallback, null));

            return asyncState;
        }
Example #18
0
        public IAsyncResult BeginSendMessage(Stream message,AsyncCallback callback,object state)
        {
            if(this.IsDisposed){
                throw new ObjectDisposedException(this.GetType().Name);
            }
            if(!this.IsConnected){
                throw new InvalidOperationException("You must connect first.");
            }
            if(message == null){
                throw new ArgumentNullException("message");
            }

            SendMessageDelegate asyncMethod = new SendMessageDelegate(this.SendMessage);
            AsyncResultState asyncState = new AsyncResultState(this,asyncMethod,callback,state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(message,new AsyncCallback(asyncState.CompletedCallback),null));

            return asyncState;
        }
Example #19
0
        /// <summary>
        /// Starts resetting session. Messages marked for deletion will be unmarked.
        /// </summary>
        /// <param name="callback">Callback to call when the asynchronous operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous operation.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when POP3 client is not connected and authenticated.</exception>
        public IAsyncResult BeginReset(AsyncCallback callback, object state)
        {
            if (IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (!IsConnected)
            {
                throw new InvalidOperationException("You must connect first.");
            }
            if (!IsAuthenticated)
            {
                throw new InvalidOperationException("The RSET command is only valid in authenticated state.");
            }

            ResetDelegate asyncMethod = Reset;
            AsyncResultState asyncState = new AsyncResultState(this, asyncMethod, callback, state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(asyncState.CompletedCallback, null));

            return asyncState;
        }
Example #20
0
        public IAsyncResult BeginStartTLS(AsyncCallback callback,object state)
        {
            if(this.IsDisposed){
                throw new ObjectDisposedException(this.GetType().Name);
            }
            if(!this.IsConnected){
                throw new InvalidOperationException("You must connect first.");
            }
            if(this.IsAuthenticated){
                throw new InvalidOperationException("The STLS command is only valid in non-authenticated state.");
            }
            if(this.IsSecureConnection){
                throw new InvalidOperationException("Connection is already secure.");
            }

            StartTLSDelegate asyncMethod = new StartTLSDelegate(this.StartTLS);
            AsyncResultState asyncState = new AsyncResultState(this,asyncMethod,callback,state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(new AsyncCallback(asyncState.CompletedCallback),null));

            return asyncState;
        }
Example #21
0
        public static IAsyncResult BeginGetDomainHosts(string domain,AsyncCallback callback,object state)
        {
            if(domain == null){
                throw new ArgumentNullException("domain");
            }
            if(string.IsNullOrEmpty(domain)){
                throw new ArgumentException("Invalid argument 'domain' value, you need to specify domain value.");
            }
            
            GetDomainHostsDelegate asyncMethod = new GetDomainHostsDelegate(GetDomainHosts);
            AsyncResultState asyncState = new AsyncResultState(null,asyncMethod,callback,state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(domain,new AsyncCallback(asyncState.CompletedCallback),null));

            return asyncState;
        }
Example #22
0
        /// <summary>
        /// Starts sending MAIL FROM: command to SMTP server.
        /// </summary>
        /// <param name="from">Sender email address reported to SMTP server.</param>
        /// <param name="messageSize">Sendable message size in bytes, -1 if message size unknown.</param>
        /// <param name="callback">Callback to call when the asynchronous operation is complete.</param>
        /// <param name="state">User data.</param>
        /// <returns>An IAsyncResult that references the asynchronous disconnect.</returns>
        /// <exception cref="ObjectDisposedException">Is raised when this object is disposed and this method is accessed.</exception>
        /// <exception cref="InvalidOperationException">Is raised when SMTP client is not connected.</exception>
        public IAsyncResult BeginMailFrom(string from, long messageSize, AsyncCallback callback, object state)
        {
            if (IsDisposed)
            {
                throw new ObjectDisposedException(GetType().Name);
            }
            if (!IsConnected)
            {
                throw new InvalidOperationException("You must connect first.");
            }

            MailFromDelegate asyncMethod = MailFrom;
            AsyncResultState asyncState = new AsyncResultState(this, asyncMethod, callback, state);
            asyncState.SetAsyncResult(asyncMethod.BeginInvoke(from,
                                                              messageSize,
                                                              asyncState.CompletedCallback,
                                                              null));

            return asyncState;
        }