.NET 8 – JSON serialize property names using snake case and kebab case

.NET 8 introduces several new naming policies that can be used with the System.Text.Json serializer. To name them:

• SnakeCaseLower
• SnakeCaseUpper
• KebabCaseLower
• KebabCaseUpper

Let’s look at the serialized output for each of them. For this, we’re going to use a Car class with the following definition:

class Car
{
    public string Make { get; set; }
    public string ModelID { get; set; }
    public int LaunchYear { get; set; }
}

And we are going to serialize the following object instance:

var car = new Car
{
    Make = "Mazda",
    ModelID = "MX-5",
    LaunchYear = 1989
};

Lower snake case (snake_case)

To serialize using lower snake_case, you need to specify JsonNamingPolicy.SnakeCaseLower as the PropertyNamingPolicy inside the serializer’s JsonSerializerOptions. Like so:

var options = new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower };
JsonSerializer.Serialize(car, options);

And the output will be:

{"make":"Mazda","model_id":"MX-5","launch_year":1989}

Upper snake case (SNAKE_CASE)

Just like above, using JsonNamingPolicy.SnakeCaseUpper as the property naming policy. The output will be:

{"MAKE":"Mazda","MODEL_ID":"MX-5","LAUNCH_YEAR":1989}

Lower kebab case (kebab-case)

To serialize using lower kebab-case, you need to specify JsonNamingPolicy.KebabCaseLower as the PropertyNamingPolicy inside the serializer’s JsonSerializerOptions. Like so:

var options = new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.KebabCaseLower };
JsonSerializer.Serialize(car, options);

This will output the following JSON:

{"make":"Mazda","model-id":"MX-5","launch-year":1989}

Upper kebab case (KEBAB-CASE)

Just like the previous example, but using JsonNamingPolicy.KebabCaseUpper for the property naming policy. You will get the following output:

{"MAKE":"Mazda","MODEL-ID":"MX-5","LAUNCH-YEAR":1989}