SmtpClient.SendAsyncCancel Method
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Cancels an asynchronous operation to send an email message.
public:
void SendAsyncCancel();public void SendAsyncCancel ();member this.SendAsyncCancel : unit -> unitPublic Sub SendAsyncCancel ()Exceptions
This object has been disposed.
Examples
The following code example demonstrates sending an email message asynchronously. The user has the option to cancel the mail if it has not been sent.
#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 be the SMTP host.
SmtpClient^ client = gcnew SmtpClient(args[1]);
// Specify the email 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 email message.
MailAddress^ to = gcnew MailAddress("ben@contoso.com");
// Specify the message content.
MailMessage^ message = gcnew MailMessage(from, to);
message->Body = "This is a test email 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)
{
client->SendAsyncCancel();
}
// Clean up.
delete message;
delete client;
client = nullptr;
Console::WriteLine("Goodbye.");
}
else
{
Console::WriteLine("Please give SMTP server name!");
}
}
using System;
using System.Net;
using System.Net.Mail;
using System.Net.Mime;
using System.Threading;
using System.ComponentModel;
namespace Examples.SmtpExamples.Async
{
public class SimpleAsynchronousExample
{
static bool mailSent = false;
private 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 != null)
{
Console.WriteLine("[{0}] {1}", token, e.Error.ToString());
} else
{
Console.WriteLine("Message sent.");
}
mailSent = true;
}
public static void Main(string[] args)
{
// Command-line argument must be the SMTP host.
SmtpClient client = new SmtpClient(args[0]);
// Specify the email sender.
// Create a mailing address that includes a UTF8 character
// in the display name.
MailAddress from = new MailAddress("jane@contoso.com",
"Jane " + (char)0xD8+ " Clayton",
System.Text.Encoding.UTF8);
// Set destinations for the email message.
MailAddress to = new MailAddress("ben@contoso.com");
// Specify the message content.
MailMessage message = new MailMessage(from, to);
message.Body = "This is a test email message sent by an application. ";
// Include some non-ASCII characters in body and subject.
string someArrows = new string(new char[] {'\u2190', '\u2191', '\u2192', '\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 += new
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.StartsWith("c") && !mailSent)
{
client.SendAsyncCancel();
}
// Clean up.
message.Dispose();
client.Dispose();
Console.WriteLine("Goodbye.");
}
}
}
Imports System.Net
Imports System.Net.Mail
Imports System.Net.Mime
Imports System.Threading
Imports System.ComponentModel
Namespace Examples.SmtpExamples.Async
Public Class SimpleAsynchronousExample
Private Shared mailSent As Boolean = False
Private Shared Sub SendCompletedCallback(ByVal sender As Object, ByVal e As AsyncCompletedEventArgs)
' Get the unique identifier for this asynchronous operation.
Dim token As String = CStr(e.UserState)
If e.Cancelled Then
Console.WriteLine("[{0}] Send canceled.", token)
End If
If e.Error IsNot Nothing Then
Console.WriteLine("[{0}] {1}", token, e.Error.ToString())
Else
Console.WriteLine("Message sent.")
End If
mailSent = True
End Sub
Public Shared Sub Main(ByVal args() As String)
' Command line argument must the SMTP host.
Dim client As New SmtpClient(args(0))
' Specify the email sender.
' Create a mailing address that includes a UTF8 character
' in the display name.
Dim mailFrom As New MailAddress("jane@contoso.com", "Jane " & ChrW(&HD8) & " Clayton", System.Text.Encoding.UTF8)
' Set destinations for the email message.
Dim mailTo As New MailAddress("ben@contoso.com")
' Specify the message content.
Dim message As New MailMessage(mailFrom, mailTo)
message.Body = "This is a test email message sent by an application. "
' Include some non-ASCII characters in body and subject.
Dim someArrows As New String(New Char() {ChrW(&H2190), ChrW(&H2191), ChrW(&H2192), ChrW(&H2193)})
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.
AddHandler client.SendCompleted, AddressOf 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.
Dim userState As String = "test message1"
client.SendAsync(message, userState)
Console.WriteLine("Sending message... press c to cancel mail. Press any other key to exit.")
Dim answer As String = Console.ReadLine()
' If the user canceled the send, and mail hasn't been sent yet,
' then cancel the pending operation.
If answer.StartsWith("c") AndAlso mailSent = False Then
client.SendAsyncCancel()
End If
' Clean up.
message.Dispose()
client.Dispose()
Console.WriteLine("Goodbye.")
End Sub
End Class
End Namespace
Remarks
Use the SendAsyncCancel method to cancel a pending SendAsync operation. If there is mail waiting to be sent, this method releases resources used to store the mail. If there is no mail waiting to be sent, this method does nothing.
Applies to
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