我正在创建一个复合WPF（Prism）应用程序，其中包括多个不同的项目（Shell、模块等）。我准备使用Log4Net实现日志记录。看起来有两种设置日志的方式：
让Shell项目进行所有实际的日志记录。它获取对Log4Net的引用，并且其他项目通过组合事件发出信号，让Shell知道需要记录某些东西。这些项目仅在Shell的app.config文件中打开了日志记录级别（DEBUG、ERROR等），以避免降低性能。
给每个项目，包括模块，提供Log4Net引用，并让项目自己记录到一个共同的日志文件中，而不是向Shell发送消息进行日志记录。
哪种方法更好？或者，是否有其他方法我应该考虑？谢谢你的帮助。
在Prism中最简单的记录日志的方式是覆盖Bootstrapper中的LoggerFacade属性。通过覆盖LoggerFacade，只要Logger实现了ILoggerFacade接口，就可以传入任何需要的Logger实例和配置信息。
我发现以下方法在记录日志方面效果很好（我使用的是Enterprise Libary Logging块，但应用于Log4Net应该也很容易）：
在你的Shell中创建一个Bootstrapper：
-My Project
-Shell Module (add a reference to the Infrastructure project)
-Bootstrapper.cs
-My Project
-Infrastructure Module
-Adapters
-Logging
-MyCustomLoggerAdapter.cs
-MyCustomLoggerAdapterExtendedAdapter.cs
-IFormalLogger.cs
MyCustomLoggerAdapter 类将用于覆盖 Bootstrapper 中的“LoggerFacade”属性。它应该有一个默认的构造函数，以创建实例。
注意：通过覆盖 Bootstrapper 中的 LoggerFacade 属性，您为 Prism 提供了记录其自身内部消息的日志机制。您可以在整个应用程序中使用此记录器，或者您可以扩展记录器以获得更完整的功能。 (请参阅 MyCustomLoggerAdapterExtendedAdapter/IFormalLogger)
public class MyCustomLoggerAdapter : ILoggerFacade
{
#region ILoggerFacade Members
/// <summary>
/// Logs an entry using the Enterprise Library logging.
/// For logging a Category.Exception type, it is preferred to use
/// the EnterpriseLibraryLoggerAdapter.Exception methods."
/// </summary>
public void Log( string message, Category category, Priority priority )
{
if( category == Category.Exception )
{
Exception( new Exception( message ), ExceptionPolicies.Default );
return;
}
Logger.Write( message, category.ToString(), ( int )priority );
}
#endregion
/// <summary>
/// Logs an entry using the Enterprise Library Logging.
/// </summary>
/// <param name="entry">the LogEntry object used to log the
/// entry with Enterprise Library.</param>
public void Log( LogEntry entry )
{
Logger.Write( entry );
}
// Other methods if needed, i.e., a default Exception logger.
public void Exception ( Exception ex ) { // do stuff }
}
MyCustomLoggerAdapterExtendedAdapter是从MyCustomLoggerAdapter派生的，可以提供额外的构造函数以实现更全面的记录器。
public class MyCustomLoggerAdapterExtendedAdapter : MyCustomLoggerAdapter, IFormalLogger
{
private readonly ILoggingPolicySection _config;
private LogEntry _infoPolicy;
private LogEntry _debugPolicy;
private LogEntry _warnPolicy;
private LogEntry _errorPolicy;
private LogEntry InfoLog
{
get
{
if( _infoPolicy == null )
{
LogEntry log = GetLogEntryByPolicyName( LogPolicies.Info );
_infoPolicy = log;
}
return _infoPolicy;
}
}
// removed backing code for brevity
private LogEntry DebugLog... WarnLog... ErrorLog
// ILoggingPolicySection is passed via constructor injection in the bootstrapper
// and is used to configure various logging policies.
public MyCustomLoggerAdapterExtendedAdapter ( ILoggingPolicySection loggingPolicySection )
{
_config = loggingPolicySection;
}
#region IFormalLogger Members
/// <summary>
/// Info: informational statements concerning program state,
/// representing program events or behavior tracking.
/// </summary>
/// <param name="message"></param>
public void Info( string message )
{
InfoLog.Message = message;
InfoLog.ExtendedProperties.Clear();
base.Log( InfoLog );
}
/// <summary>
/// Debug: fine-grained statements concerning program state,
/// typically used for debugging.
/// </summary>
/// <param name="message"></param>
public void Debug( string message )
{
DebugLog.Message = message;
DebugLog.ExtendedProperties.Clear();
base.Log( DebugLog );
}
/// <summary>
/// Warn: statements that describe potentially harmful
/// events or states in the program.
/// </summary>
/// <param name="message"></param>
public void Warn( string message )
{
WarnLog.Message = message;
WarnLog.ExtendedProperties.Clear();
base.Log( WarnLog );
}
/// <summary>
/// Error: statements that describe non-fatal errors in the application;
/// sometimes used for handled exceptions. For more defined Exception
/// logging, use the Exception method in this class.
/// </summary>
/// <param name="message"></param>
public void Error( string message )
{
ErrorLog.Message = message;
ErrorLog.ExtendedProperties.Clear();
base.Log( ErrorLog );
}
/// <summary>
/// Logs an Exception using the Default EntLib Exception policy
/// as defined in the Exceptions.config file.
/// </summary>
/// <param name="ex"></param>
public void Exception( Exception ex )
{
base.Exception( ex, ExceptionPolicies.Default );
}
#endregion
/// <summary>
/// Creates a LogEntry object based on the policy name as
/// defined in the logging config file.
/// </summary>
/// <param name="policyName">name of the policy to get.</param>
/// <returns>a new LogEntry object.</returns>
private LogEntry GetLogEntryByPolicyName( string policyName )
{
if( !_config.Policies.Contains( policyName ) )
{
throw new ArgumentException( string.Format(
"The policy '{0}' does not exist in the LoggingPoliciesCollection",
policyName ) );
}
ILoggingPolicyElement policy = _config.Policies[policyName];
var log = new LogEntry();
log.Categories.Add( policy.Category );
log.Title = policy.Title;
log.EventId = policy.EventId;
log.Severity = policy.Severity;
log.Priority = ( int )policy.Priority;
log.ExtendedProperties.Clear();
return log;
}
}
public interface IFormalLogger
{
void Info( string message );
void Debug( string message );
void Warn( string message );
void Error( string message );
void Exception( Exception ex );
}
在 Bootstrapper 中：
public class MyProjectBootstrapper : UnityBootstrapper
{
protected override void ConfigureContainer()
{
// ... arbitrary stuff
// create constructor injection for the MyCustomLoggerAdapterExtendedAdapter
var logPolicyConfigSection = ConfigurationManager.GetSection( LogPolicies.CorporateLoggingConfiguration );
var injectedLogPolicy = new InjectionConstructor( logPolicyConfigSection as LoggingPolicySection );
// register the MyCustomLoggerAdapterExtendedAdapter
Container.RegisterType<IFormalLogger, MyCustomLoggerAdapterExtendedAdapter>(
new ContainerControlledLifetimeManager(), injectedLogPolicy );
}
private readonly MyCustomLoggerAdapter _logger = new MyCustomLoggerAdapter();
protected override ILoggerFacade LoggerFacade
{
get
{
return _logger;
}
}
}
最后，要使用任意一种记录器，你只需要将相应的接口添加到你的类构造函数中，UnityContainer会为你注入记录器：
public partial class Shell : Window, IShellView
{
private readonly IFormalLogger _logger;
private readonly ILoggerFacade _loggerFacade;
public Shell( IFormalLogger logger, ILoggerFacade loggerFacade )
{
_logger = logger;
_loggerFacade = loggerFacade
_logger.Debug( "Shell: Instantiating the .ctor." );
_loggerFacade.Log( "My Message", Category.Debug, Priority.None );
InitializeComponent();
}
#region IShellView Members
public void ShowView()
{
_logger.Debug( "Shell: Showing the Shell (ShowView)." );
_loggerFacade.Log( "Shell: Showing the Shell (ShowView).", Category.Debug, Priority.None );
this.Show();
}
#endregion
}
我认为您不需要单独的日志记录模块。通过将日志记录策略添加到基础架构模块中，所有其他模块都将获得所需的引用（假设您将基础架构模块添加为其他模块的引用）。并且通过在Boostrapper中添加记录器，您可以让UnityContainer根据需要注入日志记录策略。
在CodePlex的CompositeWPF contrib项目上，还有一个使用Log4Net的简单示例（链接）。
希望对你有所帮助。
上面建议使用的LoggerFacade的问题在于，应用程序中非prism部分不知道它。我认为Logger需要更低级别和更普遍地访问，而不仅仅是在Composite框架中。
我的建议是，为什么不依赖于标准的Debug/Trace并实现自己的TraceListener呢？这样它将适用于Prism/nonPrism部分，您可以通过此实现所需的灵活性。
ILogger外观，这让我感觉很不好。 - GusdorLogManager.GetLogger(typeof(MyModule);但只有Shell将配置记录器（例如调用XmlConfigurator.Configure），使用自己的app.config。