LogPropertiesAttribute and objects containing collections or nested objects

[DoubleTK]

I'm hoping to better understand how the .NET instrumentation library works with the [LogProperties] attribute, as it's not behaving how I expect. I'm working on a project that can receive ExportLogServiceRequest messages and make them available for query. When the project receives the ExportLogServiceRequest, and/or when I query it, the data types of the Attributes properties are not what I expect. Here are the relevant code snippets:

public record FoodRecallNotice
{
    ...
    public Product? Product { get; set; }
    public List<Location> AffectedLocations { get; set; } = [];
    ...
}

public record Product
{
    public string? Description { get; set; }
    public string? Type { get; set; }
}

public record Location
{
    public string? City { get; set; }
    public string? State { get; set; }
}

The FoodRecalNotice contains both a nested object, Product, and a collection of Location objects to outline the issue.

I have a [LoggerMessage] to log this object:

[LoggerMessage(LogLevel.Critical)]
public static partial void FoodRecallNotice(this ILogger logger, [LogProperties] FoodRecallNotice foodRecallNotice);

And I log it like this:

var foodRecallNotice = new FoodRecallNotice
{
    BrandName = "Contoso",
    RecallReasonDescription = "due to a possible health risk from Listeria monocytogenes",
    CompanyName = "Contoso Fresh Vegetables, Inc.",
    Product = new Product
    {
        Description = "Salads",
        Type = "Food & Beverages"
    },
};
foodRecallNotice.AffectedLocations.AddRange(
    new Location { City = "Seattle", State = "WA"},
    new Location { City = "Denver", State = "CO"}
);
logger.FoodRecallNotice(foodRecallNotice);

Expected behavior

I expected the nested object to be serialized as a KeyValueList, and I expected the list of locations to be serialized as an ArrayValue, like so:

{
    "attributes": [
        {
            "key": "Product",
            "value": {
                "kvlistValue": {
                    "values": [
                        {
                            "key": "Description",
                            "value": {
                                "stringValue": "Salads"
                            }
                        },
                        {
                            "key": "Type",
                            "value": {
                                "stringValue": "Food & Beverages"
                            }
                        }
                    ]
                }
            }
        },
        {
            "key": "AffectedLocations",
            "value": {
                "arrayValue": {
                    "values": [
                        {
                            "kvlistValue": {
                                "values": [
                                    {
                                        "key": "City",
                                        "value": {
                                            "stringValue": "Seattle"
                                        }
                                    },
                                    {
                                        "key": "State",
                                        "value": {
                                            "stringValue": "WA"
                                        }
                                    }
                                ]
                            }
                        },
                        {
                            "kvlistValue": {
                                "values": [
                                    {
                                        "key": "City",
                                        "value": {
                                            "stringValue": "Denver"
                                        }
                                    },
                                    {
                                        "key": "State",
                                        "value": {
                                            "stringValue": "CO"
                                        }
                                    }
                                ]
                            }
                        }
                    ]
                }
            }
        }
    ]
}

Actual Behavior

Nested objects and collections are serialized to a StringValue rather than my expected ArrayValue and KeyValueList data types.

{
    "attributes": [
        {
            "key": "Product",
            "value": {
                "stringValue": "Product { Description = Salads, Type = Food & Beverages }"
            }
        },
        {
            "key": "AffectedLocations",
            "value": {
                "stringValue": "['Location { City = Seattle, State = WA }','Location { City = Denver, State = CO }']"
            }
        }
    ]
}

Am I missing something here, or is this by design?

[cijothomas]

Can you share the output of ConsoleExporter with the strong type?

[DoubleTK]

Absolutely, here it is:

LogRecord.Timestamp:               2024-12-19T18:55:57.5202990Z
LogRecord.CategoryName:            LoggingExample.Program
LogRecord.Severity:                Fatal
LogRecord.SeverityText:            Critical
LogRecord.FormattedMessage:        
LogRecord.Body:                    
LogRecord.Attributes (Key:Value):
    foodRecallNotice.AffectedLocations: ["Location { City = Seattle, State = WA }","Location { City = Denver, State = CO }"]
    foodRecallNotice.CompanyName: Contoso Fresh Vegetables, Inc.
    foodRecallNotice.RecallReasonDescription: due to a possible health risk from Listeria monocytogenes
    foodRecallNotice.Product: Product { Description = Salads, Type = Food & Beverages }
    foodRecallNotice.BrandName: Contoso
LogRecord.EventId:                 252550133
LogRecord.EventName:               FoodRecallNotice

Resource associated with LogRecord:
telemetry.sdk.name: opentelemetry
telemetry.sdk.language: dotnet
telemetry.sdk.version: 1.10.0
service.name: unknown_service:LoggingExample

Thanks!