Is there a built in way of using snake case as the naming policy for JSON in ASP.NET Core 3?

Just slight modification in pfx code to remove the dependency on Newtonsoft Json.Net.

String extension method to convert the given string to SnakeCase.

public static class StringUtils
{
    public static string ToSnakeCase(this string str)
    {
        return string.Concat(str.Select((x, i) => i > 0 && char.IsUpper(x) ? "_" + x.ToString() : x.ToString())).ToLower();
    }
}

Then in our SnakeCaseNamingPolicy we can do

public class SnakeCaseNamingPolicy : JsonNamingPolicy
{
    public static SnakeCaseNamingPolicy Instance { get; } = new SnakeCaseNamingPolicy();

    public override string ConvertName(string name)
    {
        // Conversion to other naming convention goes here. Like SnakeCase, KebabCase etc.
        return name.ToSnakeCase();
    }
}

The last step is to register our naming policy in Startup.cs

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers()            
        .AddJsonOptions(
            options => { 
                options.JsonSerializerOptions.PropertyNamingPolicy = 
                    SnakeCaseNamingPolicy.Instance;
            });
}

Using the model:

public class WeatherForecast
{
    public DateTime Date { get; set; }

    public int TemperatureCelcius { get; set; }

    public int TemperatureFahrenheit { get; set; }

    public string Summary { get; set; }
}

Json output:

{
  "date": "2019-10-28T08:26:14.878444+05:00",
  "temperature_celcius": 4,
  "temperature_fahrenheit": 0,
  "summary": "Scorching"
}

Leave a Comment