SmtpClient.SendAsync Method (MailMessage, Object)
Assembly: System (in system.dll)
public void SendAsync ( MailMessage message, Object userToken )
public function SendAsync ( message : MailMessage, userToken : Object )
Not applicable.
Parameters
- message
A MailMessage that contains the message to send.
- userToken
A user-defined object that is passed to the method invoked when the asynchronous operation completes.
| Exception type | Condition |
|---|---|
| MailMessage.From is a null reference (Nothing in Visual Basic). -or- MailMessage.To is a null reference (Nothing in Visual Basic). -or- message is a null reference (Nothing in Visual Basic). | |
| This SmtpClient has a SendAsync call in progress. -or- Host is a null reference (Nothing in Visual Basic). -or- Host is equal to the empty string (""). -or- Port is zero. | |
| This object has been disposed. | |
| The connection to the SMTP server failed. -or- Authentication failed. -or- The operation timed out. | |
| The message could not be delivered to one or more of the recipients in To, CC, or Bcc. |
To receive notification when the e-mail has been sent or the operation has been canceled, add an event handler to the SendCompleted event. You can cancel a SendAsync operation by calling the SendAsyncCancel method.
After calling SendAsync, you must wait for the e-mail transmission to complete before attempting to send another e-mail message using Send or SendAsync.
Before calling this method, the Host and Port must be set through the configuration files by setting the relevant properties, or by passing this information into the SmtpClient(String,Int32) constructor.
If the SMTP host requires credentials, you must set them before calling this method. To specify credentials, use the UseDefaultCredentials or Credentials properties.
If you receive an SmtpException exception, check the StatusCode property to find the reason the operation failed. The SmtpException can also contain an inner exception that indicates the reason the operation failed.
Your application can detect a server certificate validation error by examining the Error property passed into the SendCompletedEventHandler delegate.
The Timeout property does not have any effect on a SendAsync call.
To send mail and block while it is transmitted to the SMTP server, use one of the Send methods.
The following code example demonstrates calling this method.
#using <System.dll> using namespace System; using namespace System::Net; using namespace System::Net::Mail; using namespace System::Net::Mime; using namespace System::Threading; using namespace System::ComponentModel; static bool mailSent; static void SendCompletedCallback(Object^ sender, AsyncCompletedEventArgs^ e) { // Get the unique identifier for this asynchronous // operation. String^ token = (String^) e->UserState; if (e->Cancelled) { Console::WriteLine("[{0}] Send canceled.", token); } if (e->Error != nullptr) { Console::WriteLine("[{0}] {1}", token, e->Error->ToString()); } else { Console::WriteLine("Message sent."); } mailSent = true; } int main(array<String^>^ args) { if (args->Length > 1) { // Command line argument must the the SMTP host. SmtpClient^ client = gcnew SmtpClient(args[1]); // Specify the e-mail sender. // Create a mailing address that includes a UTF8 // character in the display name. MailAddress^ from = gcnew MailAddress("jane@contoso.com", "Jane " + (wchar_t)0xD8 + " Clayton", System::Text::Encoding::UTF8); // Set destinations for the e-mail message. MailAddress^ to = gcnew MailAddress("ben@contoso.com"); // Specify the message content. MailMessage^ message = gcnew MailMessage(from, to); message->Body = "This is a test e-mail message sent" + " by an application. "; // Include some non-ASCII characters in body and // subject. String^ someArrows = gcnew String(gcnew array<wchar_t>{L'\u2190', L'\u2191', L'\u2192', L'\u2193'}); message->Body += Environment::NewLine + someArrows; message->BodyEncoding = System::Text::Encoding::UTF8; message->Subject = "test message 1" + someArrows; message->SubjectEncoding = System::Text::Encoding::UTF8; // Set the method that is called back when the send // operation ends. client->SendCompleted += gcnew SendCompletedEventHandler(SendCompletedCallback); // The userState can be any object that allows your // callback method to identify this send operation. // For this example, the userToken is a string constant. String^ userState = "test message1"; client->SendAsync(message, userState); Console::WriteLine("Sending message... press c to" + " cancel mail. Press any other key to exit."); String^ answer = Console::ReadLine(); // If the user canceled the send, and mail hasn't been // sent yet,then cancel the pending operation. if (answer->ToLower()->StartsWith("c") && mailSent == false) { client->SendAsyncCancel(); } // Clean up. delete message; client = nullptr; Console::WriteLine("Goodbye."); } else { Console::WriteLine("Please give SMTP server name!"); } }
- SmtpPermission to connect to the SMTP server. Associated enumeration: Connect
Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.