**Course Title:** .NET MAUI App Development **Section Title:** Networking and API Integration **Topic:** Error handling and API response management **Introduction** In the previous topic, we explored how to consume APIs using HttpClient and handle JSON data with System.Text.Json. However, when dealing with APIs, errors and unexpected responses can occur. In this topic, we will discuss how to handle errors and manage API responses effectively in .NET MAUI applications. **Error Handling with HttpClient** When making HTTP requests with HttpClient, errors can occur due to various reasons such as: * Network connectivity issues * Invalid API endpoint or credentials * Server errors or downtime To handle errors with HttpClient, we can use the `try-catch` block to catch exceptions: ```csharp try { var response = await client.GetAsync("https://api.example.com/ endpoint"); response.EnsureSuccessStatusCode(); } catch (HttpRequestException ex) { // Handle network errors Console.WriteLine($"Network error: {ex.Message}"); } catch (Exception ex) { // Handle other errors Console.WriteLine($"Error: {ex.Message}"); } ``` **Handling API Response Status Codes** APIs use HTTP status codes to indicate the result of a request. Here are some common status codes: * 200 OK: Successful request * 400 Bad Request: Invalid request * 401 Unauthorized: Authentication failed * 404 Not Found: Resource not found * 500 Internal Server Error: Server error We can use the `EnsureSuccessStatusCode()` method to throw an exception if the status code is not successful (200-299): ```csharp var response = await client.GetAsync("https://api.example.com/ endpoint"); response.EnsureSuccessStatusCode(); ``` Alternatively, we can check the status code manually: ```csharp var response = await client.GetAsync("https://api.example.com/ endpoint"); if (response.IsSuccessStatusCode) { // Successful request } else { // Handle error Console.WriteLine($"Error: {response.StatusCode}"); } ``` **API Response Serialization** When receiving data from an API, we need to deserialize the JSON response into a C# object. We can use the `System.Text.Json` namespace to deserialize JSON: ```csharp var response = await client.GetAsync("https://api.example.com/ endpoint"); var json = await response.Content.ReadAsStringAsync(); var data = JsonSerializer.Deserialize<MyData>(json); ``` **Error Handling Strategies** Here are some strategies for handling errors in .NET MAUI applications: * **Retry policies**: Implement a retry policy to retry failed requests after a certain delay. * **Error logging**: Log errors to a database or file for debugging and analysis. * **User notification**: Notify the user of errors and provide a friendly error message. **Best Practices** * **Handle specific exceptions**: Catch specific exceptions instead of catching the general `Exception` class. * **Log errors**: Log errors to a database or file for debugging and analysis. * **Test error handling**: Test error handling scenarios to ensure that your application behaves correctly. **Example Use Case** Let's say we are building a .NET MAUI application that consumes a weather API. The API returns a JSON response with the current weather conditions. We want to handle errors and display a friendly error message to the user. ```csharp try { var response = await client.GetAsync("https://api.weather.com/ endpoint"); response.EnsureSuccessStatusCode(); var json = await response.Content.ReadAsStringAsync(); var weatherData = JsonSerializer.Deserialize<WeatherData>(json); // Display weather data to the user } catch (HttpRequestException ex) { Console.WriteLine($"Network error: {ex.Message}"); // Display error message to the user } catch (Exception ex) { Console.WriteLine($"Error: {ex.Message}"); // Display error message to the user } ``` **Conclusion** In this topic, we covered error handling and API response management in .NET MAUI applications. We discussed how to handle errors with HttpClient, handle API response status codes, and deserialize JSON responses. We also covered error handling strategies, best practices, and provided an example use case. **What's Next?** In the next topic, we will cover authentication and authorization in .NET MAUI applications. **Do you have any questions or need help with this topic?** Please leave a comment below, and we will respond as soon as possible. For more information on error handling and API response management in .NET MAUI, please refer to the following resources: * [Microsoft Documentation: Error handling with HttpClient](https://docs.microsoft.com/en-us/dotnet/api/system.net.http.httpclient?view=net-6.0#error-handling) * [Microsoft Documentation: Handling API response status codes](https://docs.microsoft.com/en-us/aspnet/core/web-api/handle-errors?view=aspnetcore-6.0#error-handling-middleware) * [System.Text.Json documentation](https://docs.microsoft.com/en-us/dotnet/api/system.text.json?view=net-6.0)