What are the differences between Newtonsoft.Json and System.Text.Json in MvvmCross

Default Behavior

- Newtonsoft.Json is more flexible and forgiving by default. It supports case-insensitive property name matching, which means it can deserialize JSON even if the property names in the JSON string do not exactly match the case of the properties in your C# class. This flexibility is beneficial for handling data from sources where the casing might not be consistent[1][4].

- System.Text.Json, on the other hand, is strict and case-sensitive by default. It requires exact matches between JSON property names and C# property names, which can lead to deserialization errors if the cases do not match. However, this strictness enhances performance and security[1][4].

Serialization and Deserialization

- Newtonsoft.Json allows for more lenient serialization and deserialization. For example, it can convert numeric values to string properties and vice versa, which is not possible with System.Text.Json out of the box. This means if your JSON contains a numeric value but your C# property is a string, Newtonsoft.Json can handle it seamlessly, whereas System.Text.Json will skip such fields[5].

- System.Text.Json adheres strictly to the JSON specification (RFC 8259) and does not support deserializing numeric values into string properties or vice versa without additional configuration. It requires explicit converters to handle such scenarios[4][5].

Character Escaping

- Newtonsoft.Json is less strict about character escaping. It allows more characters to pass through without escaping, which can be beneficial for certain scenarios but may pose security risks if not managed properly[1].

- System.Text.Json escapes more characters by default, including all non-ASCII characters and HTML-sensitive characters, to provide better protection against XSS attacks[1].

Field Support

- Newtonsoft.Json supports serializing and deserializing fields directly, which can be useful in certain scenarios where properties are not applicable.

- System.Text.Json does not support serializing or deserializing fields by default. However, starting from .NET 5, you can enable field serialization by setting `JsonSerializerOptions.IncludeFields` to `true` or by using the `[JsonInclude]` attribute on specific fields[3].

Performance

- System.Text.Json is generally faster than Newtonsoft.Json, especially for large datasets, due to its focus on performance optimization[9].

Integration with MvvmCross

MvvmCross uses a wrapper around Newtonsoft.Json for JSON serialization and deserialization. This means that when using MvvmCross, you are likely working with Newtonsoft.Json's flexible behavior by default. If you choose to switch to System.Text.Json, you would need to adjust your serialization settings and possibly add custom converters to match the behavior you need[2][6].

In summary, while Newtonsoft.Json offers flexibility and compatibility with a wide range of scenarios, System.Text.Json prioritizes performance, security, and strict adherence to JSON standards. The choice between them in MvvmCross depends on your specific requirements and whether you need the flexibility of Newtonsoft.Json or the performance and security of System.Text.Json.