Skip properties by name with System.Text.Json

[folkcoder]

I am attempting to create a utility that will allow consumers to skip particular fields during serialization, using a simple string syntax (e.g., ParentObject.ChildObject.Property). However, I cannot find a way to resolve the full JSON path from a JsonTypeInfo. My solution must resolve the target property by all property names rather than their types, as it is possible in my domain model to have multiple properties that share a type but should have different handling.

Here's a brief example showing what I'm trying to do:

using System.Text.Json;
using System.Text.Json.Serialization.Metadata;

namespace TestProject1;

public class UnitTest1
{
    private record Delivery(Location Source, Location Destination);

    private record Location(string City, string State);
 
    private readonly JsonSerializerOptions _serializerOptions = new()
    {
        TypeInfoResolver = new DefaultJsonTypeInfoResolver
        {
            Modifiers = { SkipProperties },
        },
    };
 
    [Fact]
    public void Test1()
    {
        var source = new Location("New York", "NY");
        var destination = new Location("Indianapolis", "IN");
        var delivery = new Delivery(source, destination);
        
        var serialized = JsonSerializer.Serialize(delivery, _serializerOptions); 
    }
    
    private static void SkipProperties(JsonTypeInfo typeInfo)
    {
        foreach (var prop in typeInfo.Properties)
        {
            // I only want custom handling around the Delivery.Source property, not any property with the name
            // "City", so this will not work
            if (prop.Name.Equals("City", StringComparison.OrdinalIgnoreCase))
            {
                prop.ShouldSerialize = (_, _) => true;
            }
        }
    }
}

Is there anything I'm missing, or is this just not possible with System.Text.Json?

[elgonzo]

(Sorry, i deleted my former comment. I confused serialization and deserialization)

Would the object graph to be serialized suitable for serialization into a JsonNode representation (including the properties to be skipped)? If so, the JsonNode representation could then be modified (like deleting unwanted json properties), and then be written to the target buffer/stream or converted to a json string. Drawback of this procedure is that the unwanted properties will also be serialized in the JsonNode representation, which is obviously costing both some performance as well as memory, and could also introduce problems in scenarios like when using references in the serialized json data.

[folkcoder]

@elgonzo This is the plan I've landed on, following some guidance from this blog post: https://josef.codes/some-basic-query-support-for-system-text-json-jsonpath-inspired/

It works pretty well so far, but I was hoping to avoid the performance hit from the additional serializations as this code is in an area with lots of throughput. But as far as I can tell, I don't see a way to avoid it with the configurations available to me in the JSON settings.

[BreyerW]

TypeInfoResolver alone definitely wont be enough. Im not 100% sure but my guts are telling me that you could try writing custom converter that tracks at what path you are and skip writing json/delegating to actual converter when hitting correct path