WriteAsJsonAsync throws exception when using NewtonsoftJson serializer

[CSharpBender]

Description

In Azure Functions isolated model an exception is thrown when overriding the serializer from ConfigureFunctionsWebApplication() and response.WriteAsJsonAsync() is used: System.InvalidOperationException: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.
I followed the Microsoft guide for migrating an in-process Azure function to the isolated model which clearly states that I need to override the Json serializer in ConfigureFunctionsWebApplication and use services.AddMvc().AddNewtonsoftJson().
While searching for a fix to my issue I found issue1 and issue2

Steps to reproduce

1. Create an Azure Function

 [Function("MyIsolatedFunction")]
        public async Task<HttpResponseData> Run(
            [HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequestData request)
        { 
            var response = request.CreateResponse(HttpStatusCode.OK);
            await response.WriteAsJsonAsync(new { Name="Error"});
            return response;
 }

2. Override Json serializer in Program.cs

public static class Program
{
    public static void Main(string[] args)
    {
        var host = new HostBuilder()
                .ConfigureFunctionsWebApplication((IFunctionsWorkerApplicationBuilder builder) =>
                {
                    builder.Services.Configure<WorkerOptions>(workerOptions =>
                    {
                        //<PackageReference Include="Microsoft.Azure.Core.NewtonsoftJson" Version="1.0.0" />
                        var settings = NewtonsoftJsonObjectSerializer.CreateJsonSerializerSettings();
                        settings.ContractResolver = new CamelCasePropertyNamesContractResolver();
                        settings.NullValueHandling = NullValueHandling.Ignore;

                        workerOptions.Serializer = new NewtonsoftJsonObjectSerializer(settings);
                    });
                })
                .ConfigureServices(services =>
                {
                    services.AddApplicationInsightsTelemetryWorkerService();
                    services.ConfigureFunctionsApplicationInsights();
                    services.ConfigureSerializer();
                })
                .Build();

        host.Run();
    }
    public static IServiceCollection ConfigureSerializer(this IServiceCollection services)
    {
        services.AddMvc().AddNewtonsoftJson();
        return services;
    }
}

3. Exception is thrown: System.InvalidOperationException: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead.

4. If I remove this line the exception disappears but the serialization is wrong because I'm using NewtonsoftJson attributes.
   workerOptions.Serializer = new NewtonsoftJsonObjectSerializer(settings); also this breaks the swagger definition.
   Another workaround is to serialize the object myself and use the WriteAsync method instead of WriteAsJsonAsync

[snerte]

I'm having thesame exception when using:

        public async Task<HttpResponseData> HttpStart(
        [HttpTrigger(AuthorizationLevel.Anonymous, "post")] HttpRequest req,
        HttpRequestData reqData,
        [DurableClient] DurableTaskClient client)
        {
            var request = await reqData.ReadFromJsonAsync<MyModel>();

A bug for sure.

[liliankasem]

Hi, I wasn't able to repro the issue you reported. Could you try again with all the latest packages?

Here is what I tried which ended up working without issues (v1 of the worker):

csproj (functions version v4 | .net8)

  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.Core.NewtonsoftJson" Version="2.0.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.23.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.2.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.18.1" />
  </ItemGroup>

Program.cs

    public static void Main(string[] args)
    {
        var host = new HostBuilder()
                .ConfigureFunctionsWorkerDefaults((IFunctionsWorkerApplicationBuilder builder) =>
                {
                    builder.Services.Configure<WorkerOptions>(workerOptions =>
                    {
                        var settings = NewtonsoftJsonObjectSerializer.CreateJsonSerializerSettings();
                        settings.ContractResolver = new CamelCasePropertyNamesContractResolver();
                        settings.NullValueHandling = NullValueHandling.Ignore;

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

        host.Run();
    }

MyHttpFunction.cs

        [Function("MyIsolatedFunction")]
        public async Task<HttpResponseData> Run([HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequestData request)
        {
            var response = request.CreateResponse(HttpStatusCode.OK);
            await response.WriteAsJsonAsync(new { Name="Error"});
            return response;
        }

Core Tools

Azure Functions Core Tools
Core Tools Version:       4.0.6610 Commit hash: N/A +0d55b5d7efe83d85d2b5c6e0b0a9c1b213e96256 (64-bit)
Function Runtime Version: 4.1036.1.23224

[2024-11-14T22:17:04.539Z] Found /Users/likasem/source/repros/dni-newtonsoft-exception-repro/dni-newtonsoft-exception-repro.csproj. Using for user secrets file configuration.
[2024-11-14T22:17:08.219Z] Worker process started and initialized.

Functions:

        MyIsolatedFunction: [GET,POST] http://localhost:7071/api/MyIsolatedFunction

For detailed output, run func with --verbose flag.
[2024-11-14T22:17:11.409Z] Executing 'Functions.MyIsolatedFunction' (Reason='This function was programmatically called via the host APIs.', Id=7cf54d0c-a0a9-4599-a546-7cde2d241c0c)
[2024-11-14T22:17:11.934Z] Executed 'Functions.MyIsolatedFunction' (Succeeded, Id=7cf54d0c-a0a9-4599-a546-7cde2d241c0c, Duration=551ms)
[2024-11-14T22:17:13.356Z] Host lock lease acquired by instance ID '000000000000000000000000303B82C0'.

---

New Model

It's also worth noting we have a new model we suggest folks update to:

csproj (functions version v4 | .net8)

  <ItemGroup>
    <FrameworkReference Include="Microsoft.AspNetCore.App" />
    <PackageReference Include="Microsoft.Azure.Core.NewtonsoftJson" Version="2.0.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="2.0.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.2.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore" Version="2.0.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="2.0.0" />
  </ItemGroup>

Program.cs

using Azure.Core.Serialization;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Azure.Functions.Worker.Builder;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;

var builder = FunctionsApplication.CreateBuilder(args);

builder.ConfigureFunctionsWebApplication();

builder.Services.Configure<WorkerOptions>(workerOptions =>
{
    var settings = NewtonsoftJsonObjectSerializer.CreateJsonSerializerSettings();
    settings.ContractResolver = new CamelCasePropertyNamesContractResolver();
    settings.NullValueHandling = NullValueHandling.Ignore;

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

builder.Build().Run();

MyHttpFunction.cs

        [Function("MyHttpFunction")]
        public IActionResult Run([HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequest req)
        {
            _logger.LogInformation("C# HTTP trigger function processed a request.");
            return new OkObjectResult(new { Name="Error"});
        }