5. ASP .Net core - Fundamentals - Configuration

 This series is a collection of knowledge about ASP .NET Core. It just is my notes.

Part 1: Startup file.

Part 2: DI.

Part 3: Middleware.

Part 4: Host and Servers.

Part 6: Environment.

Part 7: Logs.

Part 8: Error Handling.

Part 9: Routing.

Part 10: Make an HTTP Request.

Part 11: Static files.

Part 12: Authentication and Authorization.

Part 13: CORS.

This part shows how to use configuration and how to use Options patterns.

1. Default configuration

a. ChaninedConfigurationProvider

b. appsettings.json

c. appsettings.[environment].json

d. app secrets

e. environment variables

f. command-line arguments.

Configuration providers that are added later override the previous key setting.

• JsonConfigurationProvider loads configuration in the following order:
• appsettings.json
• appsetings.{Environment}.json

=>  appsetings.{Environment}.json values override keys in appsettings.json

private readonly IConfiguration _configuration;

public WeatherForecastController(ILogger<WeatherForecastController> logger, IConfiguration configuration)

{

......

}

public WeatherForecast Get()

{

var a = new WeatherForecast

{

// Get value from configureation

Name = _configuration["Name"],

NickName = _configuration["NickName"]

};

return a;

}

2. Options pattern to read a related configuration

public class PositionOptions

{

public string Title { get; set; }

public string Name { get; set; }

}

...

var positionOptions = new PositionOptions();

Configuration.GetSection("JsonKeySection").Bind(positionOptions);

OR:

positionOptions = Configuration.GetSection(PositionOptions.Position)

.Get<PositionOptions>();

3. Combining service collection

a. How to register configures option in ConfigureServices method

• step 0: create Option class
• step 1: create extension method:
• first param: IServiveCollection
• second param: IConfiguration/ or Action<OptionClass>
• Use: services.Configure method to register configuration
• step 2: use extension method to register the service.

services.Configure<PositionOptions>( config.GetSection(PositionOptions.Position));

services.Configure<ColorOptions>( config.GetSection(ColorOptions.Color));

b. How to get value of Option at another places

• Method 1: Use: IServiceProvider serviceProvider to get option value,

Name = _serviceProvider.GetRequiredService<IOptions<PositionOption>>().Value.Name,

NickName = _serviceProvider.GetRequiredService<IOptions<PositionOption>>().Value.Position

• Method 2:

IOptions<PositionOption> _optionDelegate;

....

// Get value from Option

Name = _optionDelegate.Value.Name,

NickName = _optionDelegate.Value.Position

4. File configuration provider

• Json configuration provider
• use: config.AddJsonFile("MyConfig.json", optional: true, reloadOnChange: true)
• to add custom config json file
• This file override settings in the default configuration providers (include environment vars and command-line)
• XML configuration provider
• use: AddXmlFile

5. Others config

a. launchsetting.json

b. web.config

A sample of applying options pattern

References:

[Microsoft Learn] - Configuration

[Microsoft Learn] - Options