MacRobert.HostBuilderExtensions 1.0.27

HostBuilder Extensions

The Hostbuilder exctensions utility allows developers to decompose large appsettings.json files into smaller, environment-specific config files. This permites greater control in deployments as well as facilitating re-use of configurations between projects, so such configurations need only be modified once.

Example

public static class MyApplicationHostBuilderExtensions
{
    public static IHostBuilder AddMyApplicationSettings(this IHostBuilder hostBuilder)
    {
        return hostBuilder
            .AddAllowedHostsSettings()
            .AddConnectionStrings()
            .AddOtherSettings()...;
    }

    public const string AppSettingsRoot = "appsettings";

    //////////////////////////////////////////////////////////////////////////////////////////
    // Allowed Hosts

    private const string AllowedHostsSettingsJsonPathFormat = "allowed_hosts.{0}.json";
    private const string AllowedHostsSettingsJsonPath = "allowed_hosts.json";

    private static IHostBuilder AddAllowedHostsSettings(
        this IHostBuilder hostBuilder,
        bool optional = true,
        bool reloadOnChange = true)
    {
        return hostBuilder.AddSettings(
            AllowedHostsSettingsJsonPath,
            AllowedHostsSettingsJsonPathFormat,
            AppSettingsRoot,
            optional,
            reloadOnChange);
    }

    //////////////////////////////////////////////////////////////////////////////////////////
    // Connection Strings

    private const string ConnectionStringsJsonPathFormat = "connection_strings.{0}.json";
    private const string ConnectionStringsJsonPath = "connection_strings.json";

    private static IHostBuilder AddConnectionStrings(
        this IHostBuilder hostBuilder,
        bool optional = true,
        bool reloadOnChange = true)
    {
        return hostBuilder.AddSettings(
            ConnectionStringsJsonPath,
            ConnectionStringsJsonPathFormat,
            AppSettingsRoot,
            optional,
            reloadOnChange);
    }

    // ...
}

We can have different allowedhosts as well as different connection strings by environment each prescribing unique settings, all stored in a common 'appsettings' folder.

So for allowed-hosts we might say appsettings/allowed_hosts.json

{
  "AllowedHosts": "*"
}

For the production environment: appsettings/allowed_hosts.Production.json

{
  "AllowedHosts": "*.myapplication.io;myapplication.io"
}

In the example above, where an environment file is not defined, it will defer/cascade to the default, so Developent and Staging environments will yield * where production will only permit subdomain and main domain requests.

The resulting BuilderExtension extension method would be invoked as shown:

    var builder = WebApplication.CreateBuilder(args);
    builder.Host
        .AddXxx()
        ...
        .AddMyApplicationSettings();

Which will load the appropriate appsetting files by environment.