program.cs

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

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureAppConfiguration((ctx, config) =>
            {
                var builtConfig = config.Build();
                var keyVaultEndpoint = builtConfig["KeyVaultEndpoint"];
                var secretClient = new SecretClient(
                    new Uri(keyVaultEndpoint),
                    new Azure.Identity.ManagedIdentityCredential());
                config.AddAzureKeyVault(secretClient, new KeyVaultSecretManager())
            })
            .ConfigureWebHostDefaults(builder => builder.UseStartup<Startup>());
}