contracts.cs

private readonly Random _random = new Random();
public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services
        .AddMvc()
        .AddJsonOptions(options =>
            options.SerializerSettings.ContractResolver = _random.Next(0, 2) == 0 ? new DefaultContractResolver() : new CamelCasePropertyNamesContractResolver());
}