[WPF]在WPF中使用ObservableCollections显示Microsoft.Extensions.Logging的日志信息

梁宁 · 2025-7-21 11:50:51

背景

先前一段时间用RichTextBox实现了Microsoft.Extension.Logger的日志显示。虽然是用RichTextBox总感觉哪里不对劲，想要添加过滤显得非常复杂。最近了解并学习了ObservableCollection这个库（有点火星救援了啊），遂想到了一个更好的实现方式。
引入ObservableCollections库

在包管理中引入ObservableCollections库

可观察的日志

首先定义一个Log实体LogMessage。为了后面更好实现Filiter功能，添加LogLevel，EventId等属性。
在应用程序运行期间，需要有个存储LogMessage的地方，这里定义接口ILogMessageHolder, 使用ObservableFixedSizeRingBuffer做容器（环形数组，可以使用指定大小的size），整个Observable Logs就是这个ObservableCollections库里的容器。

public struct LogMessage
{
public LogLevel LogLevel { get; set;}
public EventId EventId { get; set;}
public string Category { get; set;}
public DateTime Time { get; set;}
public string Message { get; set;}
}
public interface ILoggerMessageHolder
{
public ObservableFixedSizeRingBuffer<LogMessage> LogMessages {get;}
}

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实现Logger等其他东西

实现LogMessageProcessor, 这里依然参照ConsoleLoggerProcessor的实现。（有个疑问，直接往LogMessage容器里添加新项，性能能开销应该不大，这里还需要使用工作线程来执行Enqueue操作吗?）

internal class LogMessageProcessor
{
//... 省略字段和其余方法实现
public LogMessageProcessor(ILogMessageHolder logMessageHolder, LoggerQueueFullMode fullMode, int maxQueueLength)
{
_logMessageHolder = logMessageHolder;
_messageQueue = new();
FullMode = fullMode;
MaxQueueLength = maxQueueLength;
_outputThread = new Thread(ProcessMessageQueue)
{
IsBackground = true,
Name = "LogMessage queue processing thread"
};
_outputThread.Start();
}
//将 WriteMessage 中写入Console的部分修改为往LogMessage容器里添加LogMessage
internal void WriteMessage(LogMessage message)
{
try
{
_logMessageHolder.LogMessages.AddLast(message);
}
catch
{
CompleteAdding();
}
}
}

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实现Logger。其实这里的LogFormatter属性可要可不要，因为这里的Formatter只对TState做格式化，可以直接做成一个内部的格式化器。当然，这里使用LogFormatter方便后期直接在配置中直接替换实现

internal class Logger : ILogger
{
private readonly string _category;
private readonly LogMessageProcessor _processor;
private StringWriter? t_stringWriter;
internal IExternalScopeProvider ScopeProvider { get; set; }
public Logger(string category, LogMessageProcessor processor, LogFormatter formatter,IExternalScopeProvider scopeProvider)
{
_category = category;
_processor = processor;
Formatter = formatter;
ScopeProvider = scopeProvider;
}
public LogFormatter Formatter { get; set; }
public IDisposable? BeginScope<TState>(TState state) where TState : notnull
{
return ScopeProvider.Push(state) ?? NullScope.Instance;
}
public bool IsEnabled(LogLevel logLevel)
{
return true;
}
public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
{
t_stringWriter ??= new StringWriter();
var entry = new LogEntry<TState>(logLevel, _category, eventId, state, exception, formatter);
Formatter.Write(entry, t_stringWriter);
var sb = t_stringWriter.GetStringBuilder();
var computedString = sb.ToString();
sb.Clear();
_processor.WriteMessage(new LogMessage()
{
Time = DateTime.Now,
Id = eventId,
Level = logLevel,
Category = _category,
Message = computedString,
});
}
}

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实现LoggerProvider和LoggingBuilderExtension

internal class LoggerProvider : ILoggerProvider
{
private readonly LogFormatter _formatter;
private readonly ConcurrentDictionary<string, Logger> _loggers = [];
private readonly LogMessageProcessor _processor;
public LoggerProvider(ILogMessageHolder holder, LogFormatter formatter)
{
_formatter = formatter;
_processor = new LogMessageProcessor(holder, LoggerQueueFullMode.Wait, 2500);
}
public ILogger CreateLogger(string categoryName)
{
return _loggers.GetOrAdd(categoryName, new Logger(categoryName, _processor, _formatter));
}
public void Dispose()
{
_processor.Dispose();
}
}
public static class LoggingBuilderExtension
{
public static ILoggingBuilder AddObservableLogs(this ILoggingBuilder builder)
{
builder.Services.AddSingleton<ILoggerProvider, LoggerProvider>();
builder.Services.AddSingleton<IMfgLoggerProvider, LoggerProvider>();
builder.Services.AddTransient<LogFormatter, SimpleLogFormatter>();
builder.Services.AddSingleton<ILogMessageHolder, LogMessageHolder>();
return builder;
}
}

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至此，Logger的核心已经完成，接下来是在View中显示Log

简单实现LogViewer

创建LogWindow,使用ItemsControl显示LogMessage。
实际上，LogMessage的Formatter，是下文的LogMessageConverter。

public class LogMessageConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is not LogMessage message)
{
return "";
}
return $"{message.Time:yyyy-MM-dd HH:mm:ss,fff} {GetLogLevelString(message.LogLevel)}: {message.Category} [{message.EventId}]\r\n{message.Message}";
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
private static string GetLogLevelString(LogLevel logLevel) => logLevel switch
{
LogLevel.Trace => "trce",
LogLevel.Debug => "dbug",
LogLevel.Information => "info",
LogLevel.Warning => "warn",
LogLevel.Error => "fail",
LogLevel.Critical => "crit",
_ => throw new ArgumentOutOfRangeException(nameof(logLevel))
};
}

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<ItemsControl ItemsSource="{Binding LogMessages}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding ., Converter={StaticResource LogMessageConverter}}"></TextBlock>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>

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创建LogWindow的DataContext
这里就涉及到ObservableCollections库的知识了，最后绑定到View上的是LogMessages属性。如果想对LogMessages进行过滤，比如选取LogLevel.Information等，使用_viewList的AttachFiliter就好啦。

public class LogWindowViewModel
{
private readonly ISynchronizedView<LogMessage, LogMessage> _viewList;
private readonly ILogMessageHolder _logMessageHolder;
public LogWindowViewModel(ILogMessageHolder logMessageHolder)
{
_logMessageHolder = logMessageHolder;
_viewList = logMessageHolder.LogMessages.CreateView(x => x);
LogMessages = _viewList.ToNotifyCollectionChanged();
}
public INotifyCollectionChangedSynchronizedViewList<LogMessage> LogMessages { get; }
}

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结尾

使用ObservableCollections可以非常简单的将LogMessage显示到某个UI上，并且LogMessages的生命周期是跟随应用程序，随时可以打开查看应用程序的日志。由于ObservableCollections是纯C#实现，理论上是可以在Avalonia中使用的。

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