Could not bind to enums when using Newtonsoft.Json

[Zoe1808]

Description

We've set the serializer to newtonsoft.Json, and got below exceptions when binding to an enum:

[Function("Echo")]
public async Task<HttpResponseData> SampleFunction(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "echo/{type}")]
    HttpRequestData req,
    TypeEnum type)

Exception: Microsoft.Azure.Functions.Worker.FunctionInputConverterException: Error converting 1 input parameters for Function 'Echo': Cannot convert input parameter 'type' to type 'xxx.TypeEnum' from type 'System.String'. Error:Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: T. Path '', line 0, position 0.
[2024-02-18T08:57:50.775Z]    at Newtonsoft.Json.JsonTextReader.ParseValue()
[2024-02-18T08:57:50.777Z]    at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)
[2024-02-18T08:57:50.779Z]    at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
[2024-02-18T08:57:50.780Z]    at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
[2024-02-18T08:57:50.782Z]    at Newtonsoft.Json.JsonSerializer.Deserialize(JsonReader reader, Type objectType)
[2024-02-18T08:57:50.788Z]    at Newtonsoft.Json.JsonSerializer.Deserialize(TextReader reader, Type objectType)
[2024-02-18T08:57:50.790Z]    at Azure.Core.Serialization.NewtonsoftJsonObjectSerializer.Deserialize(Stream stream, Type returnType, CancellationToken cancellationToken)
[2024-02-18T08:57:50.792Z]    at Azure.Core.Serialization.NewtonsoftJsonObjectSerializer.DeserializeAsync(Stream stream, Type returnType, CancellationToken cancellationToken)
[2024-02-18T08:57:50.795Z]    at Microsoft.Azure.Functions.Worker.Converters.JsonPocoConverter.GetConversionResultFromDeserialization(Byte[] bytes, Type type) in D:\a\_work\1\s\src\DotNetWorker.Core\Converters\JsonPocoConverter.cs:line 66
[2024-02-18T08:57:50.797Z]    at Microsoft.Azure.Functions.Worker.Context.Features.DefaultFunctionInputBindingFeature.BindFunctionInputAsync(FunctionContext context) in D:\a\_work\1\s\src\DotNetWorker.Core\Context\Features\DefaultFunctionInputBindingFeature.cs:line 94

For TypeEnum, I've added a json converter.

using Newtonsoft.Json;
using Newtonsoft.Json.Converters;
using Newtonsoft.Json.Serialization;

[JsonConverter(typeof(StringEnumConverter), typeof(CamelCaseNamingStrategy))]
public enum TypeEnum
{
    TypeA,
    TypeB
}

Steps to reproduce

see description.

[liliankasem]

@Zoe1808 can you share how you're configuring the serializer? Sharing the program.cs file should help

[Zoe1808]

Hi @liliankasem
We just call this extension method to configure the serializer.

internal static IFunctionsWorkerApplicationBuilder UseNewtonsoftJson(this IFunctionsWorkerApplicationBuilder builder)
{
    builder.Services.Configure<WorkerOptions>(workerOptions =>
    {
        var settings = NewtonsoftJsonObjectSerializer.CreateJsonSerializerSettings();
        settings.NullValueHandling = NullValueHandling.Ignore;

        workerOptions.Serializer = new NewtonsoftJsonObjectSerializer(settings);
    });

    return builder;
}

We also tried to add the converter, but did not work.

settings.Converters.Add(new Newtonsoft.Json.Converters.StringEnumConverter());

[liliankasem]

it looks like we don't have an Enum converter so I do not expect this to work. As for using Newtonsoft/System.Text - I don't think they support plain Enum deserialization, it would need to be part of a POCO. I.e.

public class Item
{
    EnumType Type { get; set; }
}

If you do want it to work exactly with an Enum binding, you could write your own converter and register it. We don't have any official docs for that but this blog post outlines the steps for this:

• https://techiesweb.net/2023/02/11/azure-functions-input-converters.html

[kshyju]

Here is a sample app with a custom converter implementation which binds to the enum.

https://github.com/kshyju/MoreDotnetIsolatedSamples/tree/master/EnumInputConverter

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This issue has been automatically marked as stale because it has been marked as requiring author feedback but has not had any activity for 4 days. It will be closed if no further activity occurs within 3 days of this comment.

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[microsoft-github-policy-service]

This issue has been automatically marked as stale because it has been marked as requiring author feedback but has not had any activity for 4 days. It will be closed if no further activity occurs within 3 days of this comment.