Serilog WriteTo.Conditional在Azure函数中无日志输出求助

开发基于.NET 6.0独立版的C# HTTP触发Azure函数，尝试通过Serilog将日志输出到控制台、文件、两个数据库表这多个目标。单独测试WriteTo.Console、WriteTo.File、WriteTo.MSSqlServer均正常，但使用WriteTo.Conditional按日志级别配置条件输出后，所有目标均无日志输出。已开启Serilog Self Log但未捕获到任何信息。

相关代码如下：

Program.cs配置 #

var logger = new LoggerConfiguration()
    .MinimumLevel.Debug()
    .WriteTo.Conditional(
        ev =>
        {
            bool isDebug = ev.Equals(LogEventLevel.Debug);
            if (isDebug) { return true; }
            return false;
        },
        wt => wt
            .Console()
        )
    .WriteTo.Conditional(
        ev =>
        {
            bool isDebug = ev.Equals(LogEventLevel.Debug);
            if (isDebug) { return true; }
            return false;
        },
        wt => wt
            .File("log.txt")
        )
    .WriteTo.Conditional(
        ev => {
            bool isInformation = ev.Equals(LogEventLevel.Information);
            if (isInformation) { return true; }
            return false;
        },
        wt => wt
            .MSSqlServer(
                connectionString: dbConnection,
                sinkOptions: sinkOptsHead,
                columnOptions: columnOptsHead
            )
        )
    .WriteTo.Conditional(
        ev => {
            bool isWarning = ev.Equals(LogEventLevel.Warning);
            if (isWarning) { return true; }
            return false;
        },
        wt => wt
            .MSSqlServer(
                connectionString: dbConnection,
                sinkOptions: sinkOptsDetails,
                columnOptions: columnOptsDetails
            )
        )
    .CreateLogger();

Serilog Self Log配置 #

Serilog.Debugging.SelfLog.Enable(msg =>
{
    Debug.Print(msg);
    Debugger.Break();
});

函数内日志调用代码 #

logger.LogDebug("C# HTTP trigger function processed a request.");
logger.LogInformation("{GLOBAL_UUID}{USE_CASE}{ORDER_STATUS}{TIMESTAMP}", guid, useCase, orderStatus, DateTime.Now);
logger.LogWarning("{GLOBAL_UUID}{USE_CASE}{REQUEST_UUID}{SERVICE}{END_SYSTEM}{STATE}{PAYLOAD}{TIMESTAMP}{LEVEL_TYPE}", 
                  guid, useCase, Guid.NewGuid(), service, context.GetType, orderStatus, req.Body, DateTime.Now, levelType);

核心问题在于WriteTo.Conditional的条件判断逻辑错误：

• Conditional委托的参数ev是**LogEvent对象**，不是LogEventLevel枚举值。直接用ev.Equals(LogEventLevel.Debug)做判断，永远会返回false，导致所有条件分支都不触发日志输出。

修改方法是通过LogEvent的Level属性来判断日志级别，修正后的配置代码如下：

var logger = new LoggerConfiguration()
    .MinimumLevel.Debug()
    .WriteTo.Conditional(
        ev => ev.Level == LogEventLevel.Debug,
        wt => wt.Console()
    )
    .WriteTo.Conditional(
        ev => ev.Level == LogEventLevel.Debug,
        wt => wt.File("log.txt")
    )
    .WriteTo.Conditional(
        ev => ev.Level == LogEventLevel.Information,
        wt => wt.MSSqlServer(
            connectionString: dbConnection,
            sinkOptions: sinkOptsHead,
            columnOptions: columnOptsHead
        )
    )
    .WriteTo.Conditional(
        ev => ev.Level == LogEventLevel.Warning,
        wt => wt.MSSqlServer(
            connectionString: dbConnection,
            sinkOptions: sinkOptsDetails,
            columnOptions: columnOptsDetails
        )
    )
    .CreateLogger();

额外优化建议：

• 合并相同级别的条件输出，减少重复代码：比如将Debug级别的控制台和文件输出放在同一个Conditional中，通过Sink组合多个目标

.WriteTo.Conditional(
    ev => ev.Level == LogEventLevel.Debug,
    wt => wt.Sink(new ConsoleSink())
            .Sink(new FileSink("log.txt", new JsonFormatter()))
)

• 确保Azure函数的文件输出路径有效：可以使用函数根目录路径避免权限问题

var logFilePath = Path.Combine(Environment.GetEnvironmentVariable("HOME") ?? "", "log.txt");
// 将logFilePath传入WriteTo.File

内容的提问来源于stack exchange，提问作者user3120487