Program.cs

using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;

namespace questions4me_apirestful_net
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                })
                .ConfigureAppConfiguration((ContextBoundObject, config) => {

                    // Build the current set of configuration to load values from
                    // JSON files and environment variables, including VaultName.
                    var builtConfig = config.Build();

                    // Use VaultName from the configuration to create the full vault URL.
                    var vaultUrl = $"https://{builtConfig["KeyVaultName"]}.vault.azure.net/";

                    // Load all secrets from the vault into configuration. This will automatically
                    // authenticate to the vault using a managed identity. If a managed identity
                    // is not available, it will check if Visual Studio and/or the Azure CLI are
                    // installed locally and see if they are configured with credentials that can
                    // access the vault.
                    config.AddAzureKeyVault(vaultUrl);
                });
    }
}