创立自己设置的事件接收器-Semantic Logging

创立自己设置的事件接收器

Semantic Logging Application Block提供了大量的事件接收器，如Rolling Flat File，SQL Database， 云存储接收器等。这些接收器都实现了IObservable<EventEntry>接口。

有时这些并不能很好的满足用户需求，这时就需要定制事件接收器，比方邮件接收器、短信接收器等。

下面详情以下如何定制邮件接收器，在特定的事件发生时自动发送邮件给指定的用户。

本文详情了以下主题：

创立自己设置接收器

在进程内使用自己设置接收器

创立自己设置接收器

要创立自己设置接收器，必需实现IObservable<EventEntry>接口，该接口提供了3个函数：OnCompleted，OnError和OnExt

public interface IObserver

{

void OnCompleted();

void OnError(Exception error);

void OnNext(T value);

}

下面的展现了如何创立自己设置的Email接收器。

public sealed class EmailSink : IObserver

{

private const string DefaultSubject = “Email Sink Extension”;

private IEventTextFormatter formatter;

private MailAddress sender;

private MailAddressCollection recipients = new MailAddressCollection();

private string subject;

private string host;

private int port;

private NetworkCredential credentials;

public EmailSink(string host, int port,

string recipients, string subject, string credentials,

IEventTextFormatter formatter)

{

this.formatter = formatter ?? new EventTextFormatter();

this.host = host;

this.port = GuardPort(port);

this.credentials = CredentialManager.GetCredentials(credentials);

this.sender = new MailAddress(this.credentials.UserName);

this.recipients.Add(GuardRecipients(recipients));

this.subject = subject ?? DefaultSubject;

}

public void OnNext(EventEntry entry)

{

if (entry != null)

{

using (var writer = new StringWriter())

{

this.formatter.WriteEvent(entry, writer);

Post(writer.ToString());

}

}

}

public void OnCompleted() {

}

public void OnError(Exception error) {

}

private void Post(string body)

{

using (var client = new SmtpClient(this.host, this.port)

{ Credentials = this.credentials, EnableSsl = true })

using (var message = new MailMessage(this.sender, this.recipients[0])

{ Body = body, Subject = this.subject })

{

for (int i = 1; i < this.recipients.Count; i++)

message.CC.Add(this.recipients[i]);

try

{

client.Send(message);

}

catch (SmtpException e)

{

SemanticLoggingEventSource.Log.CustomSinkUnhandledFault(

“SMTP error sending email: ” + e.Message);

}

catch (InvalidOperationException e)

{

SemanticLoggingEventSource.Log.CustomSinkUnhandledFault(

“Configuration error sending email: ” + e.Message);

}

catch (…)

{

// additional exception handling code here.

}

}

}

private static int GuardPort(int port)

{

if (port < 0)

throw new ArgumentOutOfRangeException(“port”);

return port;

}

private static string GuardRecipients(string recipients)

{

if (recipients == null)

throw new ArgumentNullException(“recipients”);

if (string.IsNullOrWhiteSpace(recipients))

throw new ArgumentException(

“The recipients cannot be empty”, “recipients”);

return recipients;

}

}

并使用一个扩展函数来实例化监听器，代码如下

public static class EmailSinkExtensions

{

public static EventListener CreateListener(string host, int port,

string recipients, string subject, string credentials,

IEventTextFormatter formatter = null)

{

var listener = new ObservableEventListener();

listener.LogToEmail(host, port, recipients, subject, credentials, formatter);

return listener;

}

public static SinkSubscription LogToEmail(

this IObservable eventStream, string host, int port,

string recipients, string subject, string credentials,

IEventTextFormatter formatter = null)

{

var sink = new EmailSink(host, port, recipients, subject, credentials, formatter);

var subscription = eventStream.Subscribe(sink);

return new SinkSubscription(subscription, sink);

}

}

如何使用自己设置接收器

private void ButtonBase_OnClick(object sender, RoutedEventArgs e)

{

var listener = new ObservableEventListener();

listener.LogToEmail(“smtp.live.com”, 25, “XXXX@163.com”, “In Proc Sample”, “etw”);

listener.EnableEvents(MyCompanyEventSource.Log,EventLevel.LogAlways, EventKeywords.All);

MyCompanyEventSource.Log.Startup();

}