C#相当于Python的日志库

Question

使用 python，我可以使用 logging 库，非常方便。

什么是 C# 的日志库？

Answer 1

您可以使用log4net 或TraceListener。

Answer 2

您还应该考虑使用 NLog (http://nlog-project.org)，因为 log4net 自 2006 年 4 月以来就没有更新过。这是关于 .NET 日志记录的另一个讨论 - log4net vs. Nlog

Answer 3

log4net 并在EntLib 中记录应用程序块，除了我听说 log4net 中有一些并发问题。

Answer 4

我发现 log4net 非常方便：http://logging.apache.org/log4net/index.html

或者，如果您想记录到事件日志，请使用跟踪侦听器。很多例子可以通过http://www.google.se/search?sourceid=chrome&ie=UTF-8&q=c%23+tracelistener找到

Answer 5

以下是来自 Python 的 logging 模块的许多概念和特性的 C# 近似：

public class Logger {
    private static readonly System.Collections.Generic.Dictionary<string, Logger> Loggers = new System.Collections.Generic.Dictionary<string, Logger>();

    private readonly string _name;
    private LoggingLevel _level;
    private readonly System.Collections.Generic.List<Filter> _filters;
    private readonly System.Collections.Generic.List<Handler> _handlers;

    public static Logger GetLogger(string name = "root") {
        Logger value;
        if (Logger.Loggers.TryGetValue(name, out value)) {
            return value;
        }
        value = new Logger(name);
        Logger.Loggers.Add(name, value);
        return value;
    }

    private Logger(string name) {
        this._name = name;
        this._level = LoggingLevel.Warning;
        this._filters = new System.Collections.Generic.List<Filter>();
        this._handlers = new System.Collections.Generic.List<Handler>();
    }

    public void SetLevel(LoggingLevel level) {
        this._level = level;
    }

    public void AddHandler(Handler handler) {
        this._handlers.Add(handler);
    }

    public void RemoveHandler(Handler handler) {
        this._handlers.Remove(handler);
    }

    public void AddFilter(Filter filter) {
        this._filters.Add(filter);
    }

    public void RemoveFilter(Filter filter) {
        this._filters.Remove(filter);
    }

    public void Debug(string message, [System.Runtime.CompilerServices.CallerFilePath] string filePath = "", [System.Runtime.CompilerServices.CallerLineNumber] int lineNumber = 0, [System.Runtime.CompilerServices.CallerMemberName] string memberName = "") {
        this.Log(LoggingLevel.Debug, message, null, filePath, lineNumber, memberName);
    }

    public void Info(string message, [System.Runtime.CompilerServices.CallerFilePath] string filePath = "", [System.Runtime.CompilerServices.CallerLineNumber] int lineNumber = 0, [System.Runtime.CompilerServices.CallerMemberName] string memberName = "") {
        this.Log(LoggingLevel.Info, message, null, filePath, lineNumber, memberName);
    }

    public void Warning(string message, [System.Runtime.CompilerServices.CallerFilePath] string filePath = "", [System.Runtime.CompilerServices.CallerLineNumber] int lineNumber = 0, [System.Runtime.CompilerServices.CallerMemberName] string memberName = "") {
        this.Log(LoggingLevel.Warning, message, null, filePath, lineNumber, memberName);
    }

    public void Error(string message, [System.Runtime.CompilerServices.CallerFilePath] string filePath = "", [System.Runtime.CompilerServices.CallerLineNumber] int lineNumber = 0, [System.Runtime.CompilerServices.CallerMemberName] string memberName = "") {
        this.Log(LoggingLevel.Error, message, null, filePath, lineNumber, memberName);
    }

    public void Critical(string message, [System.Runtime.CompilerServices.CallerFilePath] string filePath = "", [System.Runtime.CompilerServices.CallerLineNumber] int lineNumber = 0, [System.Runtime.CompilerServices.CallerMemberName] string memberName = "") {
        this.Log(LoggingLevel.Critical, message, null, filePath, lineNumber, memberName);
    }

    public void Exception(Exception error, string message = "", [System.Runtime.CompilerServices.CallerFilePath] string filePath = "", [System.Runtime.CompilerServices.CallerLineNumber] int lineNumber = 0, [System.Runtime.CompilerServices.CallerMemberName] string memberName = "") {
        this.Log(LoggingLevel.Error, message, error, filePath, lineNumber, memberName);
    }

    public void Log(LoggingLevel level, string message, Exception error = null, [System.Runtime.CompilerServices.CallerFilePath] string filePath = "", [System.Runtime.CompilerServices.CallerLineNumber] int lineNumber = 0, [System.Runtime.CompilerServices.CallerMemberName] string memberName = "") {
        if (this.IsEnabledFor(level)) {
            var record = new LogRecord(this._name, level, filePath, lineNumber, memberName, message, error);
            if (this._filters.All(x => x.Check(record))) {
                this._handlers.ForEach(x => x.Process(record));
            }
        }
    }

    public bool IsEnabledFor(LoggingLevel level) {
        return level >= this._level;
    }
}

public abstract class Handler {
    public static ExceptionSetting RaiseExceptions = ExceptionSetting.Write;
    private static readonly Formatter DefaultFormatter = new Formatter();

    private LoggingLevel _level;
    private readonly System.Collections.Generic.List<Filter> _filters;
    private Formatter _formatter;

    protected Handler() {
        this._level = LoggingLevel.Warning;
        this._filters = new System.Collections.Generic.List<Filter>();
        this._formatter = null;
    }

    public void SetLevel(LoggingLevel level) {
        this._level = level;
    }

    public void SetFormatter(Formatter formatter) {
        this._formatter = formatter;
    }

    public void AddFilter(Filter filter) {
        this._filters.Add(filter);
    }

    public void RemoveFilter(Filter filter) {
        this._filters.Remove(filter);
    }

    public void Process(LogRecord record) {
        if (this.IsEnabledFor(record.Level) && this._filters.All(x => x.Check(record))) {
            lock (this) {
                this.Emit(record);
            }
        }
    }

    protected abstract void Emit(LogRecord record);

    public bool IsEnabledFor(LoggingLevel level) {
        return level >= this._level;
    }

    private Formatter SafeFormatter => this._formatter ?? Handler.DefaultFormatter;

    protected string Format(LogRecord record) {
        return this.SafeFormatter.Format(record);
    }

    protected void HandleError(LogRecord record, Exception error) {
        if (Handler.RaiseExceptions != ExceptionSetting.Pass) {
            Console.Error.WriteLine("--- Logging error ---");
            Console.Error.WriteLine(error);
            Console.Error.WriteLine($"Logged from file {record.FilePath}, line {record.LineNumber}");
            Console.Error.WriteLine($"Message: {record.Message}");
            Console.Error.WriteLine($"Created: {this.SafeFormatter.FormatTime(record)}");
            if (Handler.RaiseExceptions == ExceptionSetting.Throw) {
                throw error;
            }
        }
    }
}

public class StreamHandler : Handler {
    public static readonly string Terminator = Environment.NewLine;

    protected System.IO.TextWriter Stream;

    public StreamHandler(System.IO.TextWriter stream = null) {
        this.Stream = stream ?? Console.Error;
    }

    public void Flush() {
        this.Stream.Flush();
    }

    protected override void Emit(LogRecord record) {
        try {
            var message = this.Format(record);
            this.Stream.Write(message);
            this.Stream.Write(StreamHandler.Terminator);
            this.Flush();
        } catch (Exception error) {
            this.HandleError(record, error);
        }
    }
}

public class FileHandler : StreamHandler {
    public static readonly System.Text.Encoding DefaultEncoding = System.Text.Encoding.GetEncoding("iso-8859-1");

    protected readonly string FileName;
    private readonly System.IO.FileMode _mode;
    private readonly System.Text.Encoding _codec;

    public FileHandler(string fileName, System.IO.FileMode mode, System.Text.Encoding codec = null) : base(
        new System.IO.StreamWriter(new System.IO.FileStream(fileName, mode), codec ?? FileHandler.DefaultEncoding)) {
        this.FileName = fileName;
        this._mode = mode;
        this._codec = codec;
    }

    public void Close() {
        this.Flush();
        this.Stream.Close();
    }

    protected System.IO.StreamWriter Open() {
        return new System.IO.StreamWriter(new System.IO.FileStream(this.FileName, this._mode), this._codec ?? FileHandler.DefaultEncoding);
    }
}

public abstract class BaseRotatingHandler : FileHandler {
    protected Func<string, string> Namer;
    protected Action<string, string> Rotator;

    protected BaseRotatingHandler(string fileName, System.IO.FileMode mode, System.Text.Encoding codec = null) : base(
        fileName, mode, codec) {
        this.Namer = null;
        this.Rotator = null;
    }

    protected override void Emit(LogRecord record) {
        try {
            if (this.ShouldRollover(record)) {
                this.DoRollover();
            }
            base.Emit(record);
        } catch (Exception error) {
            this.HandleError(record, error);
        }

    }

    protected abstract bool ShouldRollover(LogRecord record);

    protected abstract void DoRollover();

    protected string GetRotationFilename(string defaultName) {
        return this.Namer == null ? defaultName : this.Namer(defaultName);
    }

    protected void Rotate(string source, string destination) {
        if (this.Rotator == null) {
            System.IO.File.Move(source, destination);
        } else if (System.IO.File.Exists(source)) {
            this.Rotator(source, destination);
        }
    }
}

public class RotatingFileHandler : BaseRotatingHandler {
    private readonly int _maxBytes;
    private readonly int _backupCount;

    public RotatingFileHandler(string fileName, System.IO.FileMode mode, int maxBytes = 0, int backupCount = 0,
        System.Text.Encoding codec = null) : base(fileName, mode, codec) {
        this._maxBytes = maxBytes;
        this._backupCount = backupCount;
    }

    protected override bool ShouldRollover(LogRecord record) {
        if (this._maxBytes <= 0) return false;
        var message = $"{this.Format(record)}{StreamHandler.Terminator}";
        return ((System.IO.StreamWriter) this.Stream).BaseStream.Position + message.Length >= this._maxBytes;
    }

    protected override void DoRollover() {
        this.Close();
        if (this._backupCount > 0) {
            string destination;
            foreach (var i in Enumerable.Range(1, this._backupCount - 1).Reverse()) {
                var source = this.GetRotationFilename($"{this.FileName}.{i}");
                destination = this.GetRotationFilename($"{this.FileName}.{i + 1}");
                if (System.IO.File.Exists(source)) {
                    if (System.IO.File.Exists(destination)) {
                        System.IO.File.Delete(destination);
                    }
                    System.IO.File.Move(source, destination);
                }
            }
            destination = this.GetRotationFilename($"{this.FileName}.1");
            if (System.IO.File.Exists(destination)) {
                System.IO.File.Delete(destination);
            }
            this.Rotate(this.FileName, destination);
        }
        this.Stream = this.Open();
    }
}

public class SmtpHandler : Handler {
    private readonly System.Net.DnsEndPoint _mailServer;
    private readonly string _fromAddress;
    private readonly System.Collections.Generic.List<string> _toAddress;
    private readonly string _subject;
    private readonly int _timeout;

    public SmtpHandler(System.Net.DnsEndPoint mailServer, string fromAddress, System.Collections.Generic.List<string> toAddress, string subject, int timeout = 1000) {
        this._mailServer = mailServer;
        this._fromAddress = fromAddress;
        this._toAddress = toAddress;
        this._subject = subject;
        this._timeout = timeout;
    }

    protected string GetSubject(LogRecord record) {
        return this._subject;
    }

    protected override void Emit(LogRecord record) {
        try {
            var message = new System.Net.Mail.MailMessage { From = new System.Net.Mail.MailAddress(this._fromAddress), Subject = this.GetSubject(record), Body = this.Format(record) };
            this._toAddress.ForEach(x => message.To.Add(new System.Net.Mail.MailAddress(x)));
            using (var client = new System.Net.Mail.SmtpClient(this._mailServer.Host, this._mailServer.Port)) {
                client.Timeout = this._timeout;
                client.Send(message);
            }
        } catch (Exception error) {
            this.HandleError(record, error);
        }
    }
}

public class Filter {
    private readonly string _name;

    public Filter(string name = null) {
        this._name = name;
    }

    public bool Check(LogRecord record) {
        return this._name == null || this._name == record.Name;
    }
}

public class StyleSettings {
    public string DefaultFormat { get; }
    public string TimeToken { get; }
    public string RegexSearch { get; }
    public string PreferredFormat { get; }

    public StyleSettings(string defaultFormat, string timeToken, string regexSearch, string preferredFormat) {
        this.DefaultFormat = defaultFormat;
        this.TimeToken = timeToken;
        this.RegexSearch = regexSearch;
        this.PreferredFormat = preferredFormat;
    }
}

public class Style {
    public static readonly StyleSettings Percent = new StyleSettings("%(Message)", "%(Created)", @"%\((\w+)\)", "%(Level):%(Name):%(Message)");
    public static readonly StyleSettings StringFormat = new StyleSettings("{Message}", "{Created}", @"\{(\w+)\}", "{Level}:{Name}:{Message}");
    public static readonly StyleSettings StringTemplate = new StyleSettings("${Message}", "${Created}", @"\$\{(\w+)\}", "${Level}:${Name}:${Message}");

    private readonly StyleSettings _settings;
    private readonly string _format;

    public Style(StyleSettings settings, string format = null) {
        this._settings = settings;
        this._format = format ?? settings.DefaultFormat;
    }

    public bool UsesTime => this._format.IndexOf(this._settings.TimeToken, StringComparison.Ordinal) >= 0;

    public string Format(LogRecord record, string dateFormat = null) {
        var regex = new System.Text.RegularExpressions.Regex(this._settings.RegexSearch);
        return regex.Replace(this._format, x => Style.Replace(x, record, dateFormat));
    }

    private static string Replace(System.Text.RegularExpressions.Match match, LogRecord record, string dateFormat) {
        System.Diagnostics.Debug.Assert(match.Groups.Count == 2, "one item should be captured");
        var value = Functions.GetProperty<LogRecord, object>(record, match.Groups[1].Value);
        return value is DateTime && dateFormat != null ? ((DateTime) value).ToString(dateFormat) : value.ToString();
    }
}

public class Formatter {
    private readonly Style _style;
    private readonly string _dateFormat;

    public Formatter(string format = null, string dateFormat = null, StyleSettings settings = null) {
        var preferredSettings = settings ?? Style.StringFormat;
        this._style = new Style(preferredSettings, format ?? preferredSettings.PreferredFormat);
        this._dateFormat = dateFormat ?? Scan.DateTimeFormat;
    }

    public string FormatTime(LogRecord record, string dateFormat = null) {
        return record.Created.ToString(dateFormat ?? this._dateFormat);
    }

    public string FormatException(LogRecord record) {
        return record.Error.ToString();
    }

    public bool UsesTime => this._style.UsesTime;

    public string FormatMessage(LogRecord record) {
        return this._style.Format(record, this._dateFormat);
    }

    public string Format(LogRecord record) {
        var message = this.FormatMessage(record);
        if (record.Error != null) {
            message += StreamHandler.Terminator + this.FormatException(record);
        }
        return message;
    }
}

public class LogRecord {
    public string Name { get; }
    public LoggingLevel Level { get; }
    public string FilePath { get; }
    public int LineNumber { get; }
    public string MemberName { get; }
    public string Message { get; }
    public Exception Error { get; }
    public DateTime Created { get; }
    public int ThreadId { get; }
    public string ThreadName { get; }
    public int ProcessId { get; }
    public string ProcessName { get; }

    public LogRecord(string name, LoggingLevel level, string filePath, int lineNumber, string memberName,
        string message, Exception error = null) {
        this.Name = name;
        this.Level = level;
        this.FilePath = filePath;
        this.LineNumber = lineNumber;
        this.MemberName = memberName;
        this.Message = message;
        this.Error = error;
        this.Created = DateTime.Now;
        var thread = System.Threading.Thread.CurrentThread;
        this.ThreadId = thread.ManagedThreadId;
        this.ThreadName = thread.Name;
        var process = System.Diagnostics.Process.GetCurrentProcess();
        this.ProcessId = process.Id;
        this.ProcessName = process.ProcessName;
    }

    public override string ToString() {
        return $"<{nameof(LogRecord)}: {this.Name}, {this.Level}, {this.FilePath}, {this.LineNumber}, {this.Message}>";
    }
}

public enum LoggingLevel {
    Debug,   // Detailed information, typically of interest only when diagnosing problems.
    Info,    // Confirmation that things are working as expected.
    Warning, // An indication that something unexpected happened, or indicative of some problem in the near future (e.g. ‘disk space low’). The software is still working as expected.
    Error,   // Due to a more serious problem, the software has not been able to perform some function.
    Critical // A serious error, indicating that the program itself may be unable to continue running.
}

public enum ExceptionSetting {
    Pass,   // Do nothing about the problem.
    Write,  // Record problem on standard error.
    Throw   // Propagate the exception once written.
}

public class Scan {
    public const string DateTimeFormat = "yyyy-MM-ddTHH:mm:ss";
}

public static class Functions {
    public static TOut GetProperty<TIn, TOut>(TIn value, string name) {
        return (TOut) Functions.NotNull(value.GetType().GetProperty(name), $"{name} is not available").GetValue(value);
    }

    public static T NotNull<T>(T value, string message = null) {
        if (value == null) {
            throw new InvalidOperationException(message ?? $"{nameof(value)} may not be null");
        }
        return value;
    }
}