JsonPropertyAttribute required

public class Videogame
{
    [JsonProperty(Required = Required.Always)]
    public string Name { get; set; }

    [JsonProperty(Required = Required.AllowNull)]
    public DateTime? ReleaseDate { get; set; }
}

string json = @"{
  'Name': 'Starcraft III',
  'ReleaseDate': null
}";

Videogame starcraft = JsonConvert.DeserializeObject<Videogame>(json);

Console.WriteLine(starcraft.Name);
// Starcraft III

Console.WriteLine(starcraft.ReleaseDate);
// null