ASP.NET Core 3.0 System.Text.Json Camel Case Serialization

If you want camelCase serialization use this code in Startup.cs: (for example firstName)

services.AddControllers()
        .AddJsonOptions(options =>
        {
            options.JsonSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
        });

If you want PascalCase serialization use this code in Startup.cs: (for example FirstName)

services.AddControllers()
        .AddJsonOptions(options =>
        {
            options.JsonSerializerOptions.PropertyNamingPolicy= null;
        );

AddJsonOptions() would config System.Text.Json only for MVC. If you want to use JsonSerializer in your own code you should pass the config to it.

var options = new JsonSerializerOptions
{
    PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
};

var json = "{\"firstname\":\"John\",\"lastname\":\"Smith\"}";
var person = JsonSerializer.Parse<Person>(json, options);