Table of Contents

Configuration Integration

The Invex.Rez.Configuration package integrates Rez with Microsoft.Extensions.Configuration, enabling two complementary scenarios:

  1. Configuration as a source — use configuration values as Rez variables (ConfigResolverSource)
  2. Templates inside configuration — write Rez templates in your configuration files and have them resolved transparently when values are read (IResolvableConfig)

Installation

dotnet add package Invex.Rez.Configuration

Configuration as a variable source

ConfigResolverSource is an IResolverSource that resolves variables from an IConfigurationRoot:

appsettings.json

{
  "ServiceName": "orders-api",
  "Logging": {
    "Level": "Information"
  }
}

var config = new ConfigurationBuilder()
    .AddJsonFile("appsettings.json")
    .Build();

var resolver = new Resolver()
    .AddSource(new ConfigResolverSource(config));

resolver.Resolve("Starting {ServiceName} with log level {Logging:Level}");

// "Starting orders-api with log level Information"

Nested configuration keys are addressed using the standard colon-delimited form (e.g., {Logging:Level}), exactly as with IConfiguration indexers. This source provides variables only — it does not supply functions.

Templates inside configuration values

IResolvableConfig wraps an IConfigurationRoot so that any value read from it is resolved with an IResolver first. This lets configuration values reference each other (or anything else your resolver's sources provide):

appsettings.json

{
  "BaseUrl": "https://api.example.com",
  "Endpoints": {
    "Orders": "{BaseUrl}/orders",
    "Customers": "{BaseUrl}/customers"
  }
}

Registration with dependency injection

Use the AddResolvableConfiguration() extension method. It registers an IResolvableConfig singleton that requires IConfigurationRoot and IResolver to be registered as well:

var config = (IConfigurationRoot)new ConfigurationBuilder()
    .AddJsonFile("appsettings.json")
    .Build();

var resolver = new Resolver()
    .AddSource(new ConfigResolverSource(config));

var services = new ServiceCollection()
    .AddSingleton<IConfigurationRoot>(config)
    .AddSingleton<IResolver>(resolver)
    .AddResolvableConfiguration()
    .BuildServiceProvider();

var resolvableConfig = services.GetRequiredService<IResolvableConfig>();

var ordersUrl = resolvableConfig["Endpoints:Orders"];

// ordersUrl: "https://api.example.com/orders"

Behavior

  • Values read via the indexer, GetSection(), GetChildren(), and section Value properties are resolved automatically.
  • Child sections are wrapped too, so resolution applies at any depth.
  • Writes pass through unmodified — assigning a value stores the raw text, templates intact.
  • IResolvableConfig also exposes the Resolver used and a convenience Resolve(string?) method for resolving arbitrary text with the same resolver.
  • Since IResolvableConfig implements IConfigurationRoot, it can be handed to any API that accepts IConfiguration/IConfigurationRoot, transparently adding template resolution.

Escaping in JSON

Remember that backslashes must be escaped in JSON, so a literal brace in a configuration value is written as:

{
  "myTemplate": "\\{escapedVariable\\}"
}

Combining both scenarios

A common setup uses the configuration itself as the variable source for resolving the configuration's own values — this is exactly what the registration example above does: ConfigResolverSource feeds variables from appsettings.json into the resolver, and IResolvableConfig applies that resolver to every value read, so configuration values can reference each other freely.

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