你可以使用这个serilog扩展：
dotnet add package Serilog.Expressions
参见github serilog-expressions：条件块：你可以像... {#if Property is not null} ({Property}){#end} ...这样做

感谢@Kraego，我终于弄明白了这一点。下面是如何使用Serilog.Expressions NuGet包设置日志记录器：

var logger = new LoggerConfiguration()
            .WriteTo.Console(
                new ExpressionTemplate(
                    "{@t:yyyy-MM-dd HH:mm:ss.fff} [{@l}] {#if SourceContext is not null} ({SourceContext}){#end}\n{@m}{#if @x is not null}\n{@p}{#end}\n{@x}\n",
                    theme: TemplateTheme.Literate))
            .CreateLogger();

在我的例子中，我只想在异常的情况下打印属性（@p），否则我只想打印呈现的消息。示例用法：

logger.LogDebug("Sending {Count} records to Kafka broker for asset {AssetId}, session: {SessionId}", 1000, 1234, 5678);

logger.LogWarning(exception, "An Exception was thrown during the processing of Data Source: {DataSource}. Retry attempt {Retry}/{MaxRetries}", "MyFileName.gz", 1, 3);

以及它们相应的输出：

2023-04-13 05:34:38.543 [Debug]  [MyNamespace.Pipeline.Kafka.KafkaMessagePublisher]
Sending 1000 records to Kafka broker for asset 1234, session: 5678

2023-04-13 05:34:39.666 [Warning]  [MyNamespace.Importer.Core.Processors.ProcessorPipeline]
An Exception was thrown during the processing of Data Source: MyFileName.gz. Retry attempt 1/3
<CUSTOM EXCEPTION PROPERTIES>
<STACK TRACE>