Rez

A library to implement the parsing and resolving of template text in .NET applications.

The Basics

Rez consists of two main parts:

A specification for a simple templating language
A library implementing the parsing and resolving of Rez template text in .NET applications

Rez takes heavy inspiration from Mustache, a popular templating language used in many web applications. One of the key reasons for creating Rez instead of using an existing solution was the need for terse, nestable tokens that are still easy to read.

var resolver = new Resolver();
resolver.AddSource(new ResolverSource(new Dictionary<string, string> { { "name", "World" } }));

var greeting = resolver.Resolve("Hello, {name}!");

// greeting: "Hello, World!"

Features

Variables — {name} is replaced with its value
Functions — {repeat(abc,3)} invokes a function with the raw argument text
Nesting — {variable{number}} resolves inside-out, left-to-right
Recursion — resolved values may themselves contain placeholders (limit: 4096 recursions)
Escaping — \{literal\} excludes braces from resolution (the backslashes are preserved in the output)
Pluggable sources — layer any number of variable/function sources, first match wins
Graceful fallback — unresolvable placeholders are left in the output unchanged
High performance — pooled buffers and span-based parsing minimize allocations
Configuration integration — resolve templates inside Microsoft.Extensions.Configuration values

Installation

dotnet add package Invex.Rez

For Microsoft.Extensions.Configuration integration:

dotnet add package Invex.Rez.Configuration

Both packages target net10.0, net9.0, net8.0, and netstandard2.0.

Quick example

appsettings.json

{
  "animal1": "fox",
  "animal2": "dog",
  "color": "brown",
  "description": "lazy"
}

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

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

var output = resolver.Resolve("The quick {color} {animal1} jumped over the {description} {animal2}.");

// output: "The quick brown fox jumped over the lazy dog."

Documentation

Introduction — what Rez is and why it exists
Getting Started — install and resolve your first template
Syntax Guide — the complete template language reference
Examples — worked examples from simple to advanced
Developer Guide — abstractions, custom sources, and how resolution works
Configuration Integration — resolving templates in app configuration
API Reference — generated reference for every public type

Where did the name come from?

The name Rez is a play on the word "res" (short for "resolution"), which is the process of resolving a template. The name was chosen as it is short and memorable and is not too similar to other names in the .NET ecosystem.

License

See LICENSE.txt.

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