# Serilog
###### tags: `.NetCore`

## 配置
### Log Path

/// <summary> 存放 Log 的資料夾路徑 </summary>
public static string LogFolderPath { get; } = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "MyLog");

### Startup.cs 建構子中建立 Logger 物件

public Startup(IConfiguration configuration) {
    Configuration = configuration;

    // create serilog object
    {
        var flushInterval = TimeSpan.FromSeconds(60);
        Log.Logger = new LoggerConfiguration()
            .Enrich.FromLogContext() // 使用 LogContext ( PushProperty )
            .MinimumLevel.Debug()
            .WriteTo.File(
                path: Path.Combine(AppValueService.System.LogFolderPath, $@"{nameof(dataApi)}.txt"),
                outputTemplate: "[{Timestamp:yyyy-MM-dd HH:mm:ss.fff}][{ClientIP}][{Username}][{Level}] {Message}{NewLine}{Exception}",
                rollingInterval: RollingInterval.Day,
                flushToDiskInterval: flushInterval,
                fileSizeLimitBytes: 100 * 1024 * 1024, // 100MB
                rollOnFileSizeLimit: true,
                shared: true // Set true for multiple log write in same time.
            )
            .WriteTo.Logger(errorLogger => errorLogger
                .MinimumLevel.Error()
                .WriteTo.File(
                    path: Path.Combine(AppValueService.System.LogFolderPath, $@"{nameof(dataApi)}_ErrorOnly.txt"),
                    outputTemplate: "[{Timestamp:yyyy-MM-dd HH:mm:ss.fff}][{ClientIP}][{Username}][{Level}] {Message}{NewLine}{Exception}",
                    rollingInterval: RollingInterval.Day,
                    flushToDiskInterval: flushInterval,
                    fileSizeLimitBytes: 100 * 1024 * 1024, // 100MB
                    rollOnFileSizeLimit: true,
                    shared: true // Set true for multiple log write in same time.
                )
            )
            .WriteTo.Console( Serilog.Events.LogEventLevel.Information )
            .CreateLogger();
    }
}

### Startup.cs > public void Configure Push 帳號和IP欄位資料

public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ICommonHttpContext commonHttpContext) {
    // 將此時才能取得到的資料設置成 Property Push 到 Log，以利 OutputTemplate 書寫時取得資料
    app.Use(async (httpContext, next) => {
        var userName = commonHttpContext.IsAuthenticated() ? commonHttpContext.GetUsername() : "Guest"; //Gets user Name from user Identity  
        LogContext.PushProperty("Username", userName);
        LogContext.PushProperty("ClientIP", commonHttpContext.GetRequestIPAddress());
        await next.Invoke();
    });

    /// 略
}

## 使用時直接使用 Logger 物件就可

_logger.LogError(JsonConvert.SerializeObject(new {
            FullUrl = context.Request.GetDisplayUrl(), // 完整的網址列
            Error = errorResult, // 錯誤內容
        }, Formatting.Indented));