**Course Title:** .NET MAUI App Development **Section Title:** Networking and API Integration **Topic:** Handling JSON data with System.Text.Json **Introduction** In the previous topic, we explored how to consume RESTful APIs using HttpClient in .NET MAUI. One of the most common data formats returned by APIs is JSON (JavaScript Object Notation). In this topic, we will learn how to handle JSON data using the System.Text.Json namespace in .NET MAUI. **What is System.Text.Json?** System.Text.Json is a high-performance, low-allocating JSON serializer and deserializer for .NET. It is designed to be highly efficient and fast, making it suitable for use in production environments. **Deserializing JSON Data** To deserialize JSON data, we need to use the `JsonSerializer` class. This class takes a JSON string as input and returns an instance of the .NET type we specify. ```csharp using System.Text.Json; public class User { public int Id { get; set; } public string Name { get; set; } } string jsonString = "{\"Id\":1, \"Name\":\"John Doe\"}"; User user = JsonSerializer.Deserialize<User>(jsonString); ``` In this example, we define a `User` class with an `Id` and `Name` property. We then create a JSON string that represents a user object. We use the `JsonSerializer.Deserialize` method to convert the JSON string into an instance of the `User` class. **Serializing .NET Objects to JSON** To serialize a .NET object to JSON, we use the `JsonSerializer.Serialize` method. ```csharp User user = new User { Id = 1, Name = "John Doe" }; string jsonString = JsonSerializer.Serialize(user); ``` In this example, we create an instance of the `User` class and serialize it to a JSON string using the `JsonSerializer.Serialize` method. **Handling JSON Serialization Options** System.Text.Json provides several options for customizing the serialization and deserialization process. For example, we can use the `JsonSerializerOptions` class to specify how to handle property naming, indentation, and other serialization options. ```csharp JsonSerializerOptions options = new JsonSerializerOptions { PropertyNameCaseInsensitive = true, WriteIndented = true }; string jsonString = JsonSerializer.Serialize(user, options); ``` In this example, we create an instance of the `JsonSerializerOptions` class and set the `PropertyNameCaseInsensitive` property to `true`, which tells the serializer to ignore the case of property names when deserializing JSON data. We also set the `WriteIndented` property to `true`, which tells the serializer to format the JSON output with indentation. **Handling JSON Errors and Exceptions** System.Text.Json provides several error handling features, including the ability to handle parsing errors and serialization errors. ```csharp try { User user = JsonSerializer.Deserialize<User>(jsonString); } catch (JsonException ex) { Console.WriteLine($"Error deserializing JSON: {ex.Message}"); } ``` In this example, we use a try-catch block to catch any `JsonException` exceptions that occur during deserialization. **Conclusion** In this topic, we learned how to handle JSON data using the System.Text.Json namespace in .NET MAUI. We explored how to deserialize JSON data, serialize .NET objects to JSON, handle JSON serialization options, and handle JSON errors and exceptions. **External Resources** * [System.Text.Json documentation](https://docs.microsoft.com/en-us/dotnet/api/system.text.json) * [JSON documentation](https://www.json.org/json-en.html) **Exercise** Try deserializing a JSON string that represents a list of users. Use the `JsonSerializer.Deserialize` method to convert the JSON string into a list of `User` objects. **Comments and Questions** If you have any questions or need help with this topic, feel free to leave a comment below. **What's Next?** In the next topic, we will learn how to handle XML data using the System.Xml namespace in .NET MAUI.