Serilog不会破坏对象的集合

Question

MVC核心Web服务项目，使用AspNetCore 2.0.0和Serilogger 2.1.1。

当调用Serilog来记录集合/ IEnumerable / List对象时，它所做的就是列出对象类型。如果我们遍历集合中的项目并单独记录它们，Serilog会将它们解构为正常并且它们在我们的日志中正确显示。

基本代码示例：

List<MyResponse> results = ValidateResourceCollection(events);
_logger.LogInformation("EventController.Post response {@results}", results);

我们会得到一条这样的日志消息：

2018-06-11 10:53:35.952 -04:00 [Information] EventController.Post response "Blah.Models.Response.MyResponse, Blah.Models.Response.MyResponse"

有没有办法让Serilog正确地解构这个列表？我尝试通过实现IDestructuringPolicy来解决这个问题，但只有在有一个对象要进行解构时才会调用它。如果将对象集合用作参数，则永远不会调用IDestructuringPolicy。

Answer 1

您可以使用解构策略来记录对象集合：

public class CollectionDestructuringPolicy<T> : IDestructuringPolicy
{
    public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory,
        out LogEventPropertyValue result)
    {

        switch (value)
        {
            case City city:
                result = Destruct(city,propertyValueFactory);
                return true;
            case ICollection<T> collection:
                result = Destruct(collection,propertyValueFactory);
                return true;
        }
        result = null;
        return false;
    }

    private static LogEventPropertyValue Destruct(object collectionItem, ILogEventPropertyValueFactory propertyValueFactory)
    {
        var collectionItemPropertiesNamePerValue = new List<(string propertyName, object propertyValue)>();
        var collectionItemProperties = collectionItem.GetType().GetProperties().ToList();
        collectionItemProperties.ForEach(p => collectionItemPropertiesNamePerValue.Add((propertyName:p.Name, propertyValue:p.GetValue(collectionItem))));
        var properties = new List<LogEventProperty>(collectionItemPropertiesNamePerValue.Count);
        collectionItemPropertiesNamePerValue.ForEach(namePerValue =>
            properties.Add(new LogEventProperty(namePerValue.propertyName,
                propertyValueFactory.CreatePropertyValue(namePerValue.propertyValue))));
        LogEventPropertyValue result = new StructureValue(properties);
        return result;
    }

    private static LogEventPropertyValue Destruct(IEnumerable<T> collection,
        ILogEventPropertyValueFactory propertyValueFactory)
    {
        var elements = collection.Select(e => propertyValueFactory.CreatePropertyValue(e, true));
        LogEventPropertyValue result = new SequenceValue(elements);
        return result;
    }
}

//In Logger Factory:
public static class LoggerFactory
{
    public static Logger Create()
    {
        return new LoggerConfiguration()
            .WriteTo.Console()
            .Destructure.With<CollectionDestructuringPolicy<City>>()
            .CreateLogger();
    }
}

RMK。一个成熟的asp.net核心解决方案sample