Does JsonSchema.NET support validating while deserializing to external types?

[guythetechie]

Documentation

• I have consulted the documentation, and my question isn't answered there.

Nuget Package

JsonSchema.Net

Package Version

5.4.3

How can I help? Please provide as much context as possible.

Thanks for the great library.

If I understand the documentation correctly, deserialization with schema validation requires a [JsonSchema()] annotation on the destination type. What if we don't own the destination type though (e.g from an external class library)? Is there a way to validate and deserialize without the annotation?

My use case might actually be simpler than this. I'm trying to take a JsonObject, validate it with a predefined schema, then return a validated JsonObject. If the source JSON has extraneous properties but still passes validation, the destination JSON should only have properties from the schema. I was hoping for something like the code below, but I may be using the wrong tool for the job.

public static class ValidationHelpers
{
    private static readonly JsonSchema schema = JsonSchema.FromText("my schema text");

    public static void Validate(JsonNode? source)
    {
        var result = schema.Evaluate(source, new EvaluationOptions { OutputFormat = OutputFormat.Hierarchical});
        if (result.IsValid)
        {
            var validatedNode = result.xxx;
            Console.Write("""
                          Validation successful. Source might have extra properties, but no big deal.
                          validatedNode only has properties defined in the schema.
                          """);
        }
        else
        {
            var errorMessage = GetEvaluationErrorMessage(result);
            throw new JsonException(errorMessage);
        }
    }
}

Code of Conduct

• I agree to follow this project's Code of Conduct

[gregsdennis]

I don't have a way to do that, currently, no. However, off the top of my head, maybe a static type/schema registry would do. Something like:

ValidatingJsonConverter.Register<Point>(pointSchema);

[gregsdennis]

Here's what I've come up with:

JsonSchema PointSchema =
    new JsonSchemaBuilder()
        .Type(SchemaValueType.Object)
        .Properties(
            ("X", new JsonSchemaBuilder().Type(SchemaValueType.Integer)),
            ("Y", new JsonSchemaBuilder().Type(SchemaValueType.Integer))
        )
        .AdditionalProperties(false);

ValidatingJsonConverter.MapType<Point>(PointSchema);

Would this work for you?

[guythetechie]

I'm sorry, but I don't see MapType or Register as static methods on ValidatingJsonConverter.

If I create an instance of ValidatingJsonConverter, those aren't available either.

Am I missing a package? Here's what I have installed.
<PackageReference Include="JsonSchema.Net" Version="5.4.3" />

[gregsdennis]

Yeah, I haven't published anything. I'm getting your thoughts on whether a particular UX would work for you.

[guythetechie]

Understood. Yes, that should work. Thanks!