Solution 1:

services
    .AddMvc()
    .AddJsonOptions(options =>
    {
        options.SerializerSettings.ContractResolver
            = new Newtonsoft.Json.Serialization.DefaultContractResolver();
    });

This keeps a JSON object's name the same as .NET class property.

Solution 2:

You can configure JSON behavior this way:

public void ConfigureServices(IServiceCollection services)  
  {
      services.AddMvc()
                  .AddJsonOptions(options =>
                  {
                      options.SerializerSettings.ContractResolver =
                          new CamelCasePropertyNamesContractResolver();
                  });
  }