Serilog serializing fields

Question

If I have the following class

public class Customer
{
    public string Name;
}

and then have the following log command in Serilog

Log.Logger = new LoggerConfiguration()
    .WriteTo.Console()
    .WriteTo.Seq("http://localhost:5341")
    .CreateLogger();

var item = new Customer();
item.Name = "John";
Serilog.Log.Information("Customer {@item}", item);

The log just displays in Seq as

Customer {}

If I change the Name field to a property it works but I would prefer not to do that at this stage. Is there any way around it?

One option might be to use the ``Destructure`` configuration object on ``LoggerConfiguration``, as described here: https://github.com/serilog/serilog/wiki/Structured-Data#customizing-the-stored-data — J.N., Sep 11 '17 at 09:20

score 13 · Accepted Answer · answered Sep 11 '17 at 22:41

To do this just for the one type (recommended), you can use:

.Destructure.ByTransforming<Customer>(c => new { c.Name })

If you want to include public fields for all types, or those matching some kind of condition, you can plug in a policy to do it:

class IncludePublicFieldsPolicy : IDestructuringPolicy
{
    public bool TryDestructure(
        object value,
        ILogEventPropertyValueFactory propertyValueFactory,
        out LogEventPropertyValue result)
    {
        if (!(value is SomeBaseType))
        {
            result = null;
            return false;
        }

        var fieldsWithValues = value.GetType().GetTypeInfo().DeclaredFields
            .Where(f => f.IsPublic)
            .Select(f => new LogEventProperty(f.Name,
               propertyValueFactory.CreatePropertyValue(f.GetValue(value))));

        result = new StructureValue(fieldsWithValues);
        return true;
    }
}

The example scopes this down to look at objects derived from SomeBaseType only.

You can plug it in with:

.Destructure.With<IncludePublicFieldsPolicy>()

(I think it's likely to require some tweaking, but should be a good starting point.)

score 3 · Answer 2 · answered Feb 15 '20 at 20:16

Thanks to Nicholas Blumhardt for a good starting point. I just have a small tweak.

my class:

public class Dummy
{
    public string Field = "the field";
    public string Property { get; set; } = "the property";
}

log call:

Log.Information("Dummy = {@Dummy}", new Dummy());

IDestructuringPolicy implementation includes both fields and properties:

internal class IncludePublicFieldsPolicy : IDestructuringPolicy
{
    public bool TryDestructure(object value, ILogEventPropertyValueFactory propertyValueFactory, out LogEventPropertyValue result)
    {
        var typeInfo = value.GetType().GetTypeInfo();

        var fieldsWithValues = typeInfo
            .DeclaredFields
            .Where(f => f.IsPublic)
            .Select(f =>
            {
                var val = f.GetValue(value);
                var propval = propertyValueFactory.CreatePropertyValue(val);
                var ret = new LogEventProperty(f.Name, propval);
                return ret;
            })
        ;

        var propertiesWithValues = typeInfo
            .DeclaredProperties
            .Where(f => f.CanRead)
            .Select(f =>
            {
                var val = f.GetValue(value);
                var propval = propertyValueFactory.CreatePropertyValue(val);
                var ret = new LogEventProperty(f.Name, propval);
                return ret;
            })
        ;

        result = new StructureValue(fieldsWithValues.Union(propertiesWithValues));
        return true;
    }
}

Serilog serializing fields

2 Answers2