Access Json Serializer options to avoid serializing null in Azure Functions v3

Question

How can I setup the serializer in Azure Functions to ignore nulls when serializing?

This is a v3 function

I have tried

        JsonConvert.DefaultSettings = () => new JsonSerializerSettings
        {
            Formatting = Formatting.Indented,
            ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
            NullValueHandling = NullValueHandling.Ignore
        };

In the startup for my function

I am now starting to think that Newtonsoft isnt being used for json

How can I force Newtonsoft to be used?

Cheers

Paul

Answer 1

2023 edit

The various function (and MVC) versions have different ways of setting this up and may use Newtonsoft.Json or System.Text.Json

Links:

https://github.com/Azure/azure-functions-host/issues/5841#issuecomment-987168758

https://stackoverflow.com/a/62270924/5436889

test

Original answer (older versions)

Adapted from Add JSON Options In HTTP Triggered Azure Functions

Prerequisites

You need ensure that all prerequisites are fulfilled as mentioned here

From that docs page:

Before you can use dependency injection, you must install the following NuGet packages:

• Microsoft.Azure.Functions.Extensions
• Microsoft.NET.Sdk.Functions package version 1.0.28 or later
• Microsoft.Extensions.DependencyInjection (currently, only version 3.x and earlier supported)

Note:

The guidance in this article applies only to C# class library functions, which run in-process with the runtime. This custom dependency injection model doesn't apply to .NET isolated functions, which lets you run .NET 5.0 functions out-of-process. The .NET isolated process model relies on regular ASP.NET Core dependency injection patterns.

Code

Add Startup class to your Azure Function Project as given below:

using System;
using Microsoft.Azure.Functions.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Newtonsoft.Json;

[assembly: FunctionsStartup(typeof(MyNamespace.Startup))]
namespace MyNamespace {
    public class Startup: FunctionsStartup {
        public override void Configure(IFunctionsHostBuilder builder) {
            builder.Services.AddMvcCore().AddJsonFormatters().AddJsonOptions(options => {
                // Adding json option to ignore null values.
                options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;
            });
        }
    }
}

This will set the JSON option to ignore null values.