Enterprise Library 實戰系列（八）：記錄與檢測應用程式區塊——進階篇

前言

專案趕工導致延遲發布，請見諒。本篇涵蓋：字典式日誌、活動追蹤、事件過濾、格式客製化、自訂 Sink 與 Formatter。

一、在日誌中包含名稱-值對字典

LogEntry log = new LogEntry();
Hashtable logtable = new Hashtable();
logtable["key1"] = "value1";
logtable["key2"] = "value2";
logtable["key3"] = "value3";

log.Message = this.txt_LogMessage.Text;
log.Category = Category.General;
log.Priority = Priority.Normal;

Logger.Write(log, logtable);

二、追蹤活動並記錄上下文

使用 Tracer 類別自動記錄開始/結束時間：

using (new Tracer("UI Events"))
{
    Logger.Write("Troubleshooting message");
}

三、過濾事件

兩種過濾方式：

• 優先級過濾：設定最低優先級，低於者不記錄
  
• 類別過濾：指定記錄或排除特定類別
  

四、客製化日誌訊息格式

Formatter 接收 LogEntry 輸出格式化字串。Text Formatter 使用範本，{參數} 由 LogEntry 屬性填充。

五、建立與使用自訂 Sink

1. 參考組件：Microsoft.Practices.EnterpriseLibrary.Configuration.dll、Logging.dll、Logging.Sinks.dll、Logging.Distributor.Configuration.dll
2. 命名空間：Microsoft.Practices.EnterpriseLibrary.Configuration、Logging、Logging.Sinks、Logging.Distributor.Configuration
3. 繼承 LogSink，實作 Initialize、SendMessageCore：

public class ConsoleSink : LogSink
{
    private LoggingConfigurationView configView;

    public override void Initialize(ConfigurationView configurationView)
    {
        this.configView = configurationView as LoggingConfigurationView;
    }

    protected override void SendMessageCore(LogEntry logEntry)
    {
        CustomSinkData sinkData = (CustomSinkData)this.configView.GetSinkData(this.ConfigurationName);
        Console.WriteLine((string)sinkData.Attributes["delimiter"]);
        Console.WriteLine(FormatEntry(logEntry));
    }
}

4. 組態工具新增 Custom Sink，指定 TypeName 為 ConsoleSink
5. 加入 Attribute：delimiter = ************************
6. 建立 Destination 關聯 Formatter 與 Sink
7. 專案輸出類型設為 Console Application 執行

六、建立與使用自訂 Formatter

1. 命名空間：System.Globalization、System.IO、System.Xml、Configuration、Logging、Logging.Distributor.Configuration、Logging.Formatters
2. 繼承 ConfigurationProvider 實作 ILogFormatter，實作 Initialize、Format：

public class XmlFormatter : ConfigurationProvider, ILogFormatter
{
    private LoggingConfigurationView configView = null;

    public override void Initialize(ConfigurationView configurationView)
    {
        this.configView = (LoggingConfigurationView)configurationView;
    }

    public string Format(LogEntry log)
    {
        using (StringWriter sw = new StringWriter(CultureInfo.InvariantCulture))
        {
            XmlTextWriter w = new XmlTextWriter(sw);
            w.Formatting = Formatting.Indented;
            w.Indentation = 2;
            w.WriteStartDocument(true);
            w.WriteStartElement("logEntry");
            w.WriteAttributeString("Category", log.Category);
            w.WriteAttributeString("Priority", log.Priority.ToString(CultureInfo.InvariantCulture));
            w.WriteElementString("Timestamp", log.TimeStampString);
            w.WriteElementString("Message", log.Message);
            w.WriteElementString("EventId", log.EventId.ToString(CultureInfo.InvariantCulture));
            w.WriteElementString("Severity", log.Severity.ToString(CultureInfo.InvariantCulture));
            w.WriteElementString("Title", log.Title);
            w.WriteElementString("Machine", log.MachineName);
            w.WriteElementString("AppDomain", log.AppDomainName);
            w.WriteElementString("ProcessId", log.ProcessId);
            w.WriteElementString("ProcessName", log.ProcessName);
            w.WriteElementString("Win32ThreadId", log.Win32ThreadId);
            w.WriteElementString("ThreadName", log.ManagedThreadName);
            w.WriteEndElement();
            w.WriteEndDocument();
            return sw.ToString();
        }
    }
}

使用方式：組態工具新增 Custom Formatter，指定類型為 XmlFormatter。

結語

進階篇介紹字典日誌、活動追蹤、過濾、格式客製化、自訂 Sink/Formatter。下一篇將介紹快取區塊。