.net core appsettings code example

Example 1: .net using appsettings variables

var connectionString = ConfigurationManager.ConnectionStrings["Default"].ConnectionString;
connectionString.Expand() // returns "server=db01.mycompany.com;uid=uid;pwd=pwd;Initial Catalog=master;"

Example 2: .net using appsettings variables

<configuration>
    <appSettings>
        <add key="Domain" value="mycompany.com"/>
        <add key="ServerName" value="db01.{Domain}"/>
    </appSettings>
    <connectionStrings>
        <add name="Default" connectionString="server={ServerName};uid=uid;pwd=pwd;Initial Catalog=master;" provider="System.Data.SqlClient" />
    </connectionStrings>
</configuration>

Example 3: .net core read appsettings.json console app

class Program
{
    public static IConfigurationRoot configuration;

    static int Main(string[] args)
    {
        // Initialize serilog logger
        Log.Logger = new LoggerConfiguration()
             .WriteTo.Console(Serilog.Events.LogEventLevel.Debug)
             .MinimumLevel.Debug()
             .Enrich.FromLogContext()
             .CreateLogger();

        try
        {
            // Start!
            MainAsync(args).Wait();
            return 0;
        }
        catch
        {
            return 1;
        }
    }

    static async Task MainAsync(string[] args)
    {
        // Create service collection
        Log.Information("Creating service collection");
        ServiceCollection serviceCollection = new ServiceCollection();
        ConfigureServices(serviceCollection);

        // Create service provider
        Log.Information("Building service provider");
        IServiceProvider serviceProvider = serviceCollection.BuildServiceProvider();

        // Print connection string to demonstrate configuration object is populated
        Console.WriteLine(configuration.GetConnectionString("DataConnection"));

        try
        {
            Log.Information("Starting service");
            await serviceProvider.GetService<App>().Run();
            Log.Information("Ending service");
        }
        catch (Exception ex)
        {
            Log.Fatal(ex, "Error running service");
            throw ex;
        }
        finally
        {
            Log.CloseAndFlush();
        }
    }

    private static void ConfigureServices(IServiceCollection serviceCollection)
    {
        // Add logging
        serviceCollection.AddSingleton(LoggerFactory.Create(builder =>
        {
            builder
                .AddSerilog(dispose: true);
        }));

        serviceCollection.AddLogging();

        // Build configuration
        configuration = new ConfigurationBuilder()
            .SetBasePath(Directory.GetParent(AppContext.BaseDirectory).FullName)
            .AddJsonFile("appsettings.json", false)
            .Build();

        // Add access to generic IConfigurationRoot
        serviceCollection.AddSingleton<IConfigurationRoot>(configuration);

        // Add app
        serviceCollection.AddTransient<App>();
    }
}