SourceConfig

Introduction

SourceConfig is a code generator for objects that are built on *.json configuration files: when developer adds some file or new properties to existng json configuration file the POCO objects for this configuration generated.

It is based on Source Generators feature that has been intoduced with C# 9.0 and brings a possibility to generate code during build time.

Installation

Install using nuget package manager:

Install-Package Compentio.SourceConfig

or .NET CLI:

dotnet add package Compentio.SourceConfig

How to use

During creation of any *json file (any json files are treated as configuration files), e.g. apsetting.json the POCO representation of this json is generated:

{
  "NoteEmailAddresses": [
    "[email protected]",
    "[email protected]",
    "[email protected]"
  ],
  "ConnectionTimeout": "30",
  "ConnectionHost": "https://test.com",
  "DefaultNote": {
    "Title": "DefaultTitle",
    "Description":  "DefaultDescription"
  }
}

in that case SourceConfig generates

// <mapper-source-generated />
// <generated-at '18.10.2021 14:49:51' />
using System;
using System.Collections.Generic;

namespace Compentio.SourceConfig.App
{
    public class AppSettings
    {
        public IEnumerable<string> NoteEmailAddresses { get; set; }

        public string ConnectionTimeout { get; set; }

        public string ConnectionHost { get; set; }

        public string DatabaseSize { get; set; }

        public DefaultNote DefaultNote { get; set; }
    }

    public class DefaultNote
    {
        public string Title { get; set; }

        public string Description { get; set; }
    }
}

AppSettings is taken from the filename, Compentio.SourceConfig.App namespace is inherited from configuration file directory (here, appsettings.json is in app root directory, thus main app namespace is used).

To enable processing json files, in *.cproj project the configs should be marked as AdditionalFiles:

<ItemGroup>
  <AdditionalFiles Include="Appsettings.Development.json">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  </AdditionalFiles>
  <AdditionalFiles Include="Appsettings.json">
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  </AdditionalFiles>
</ItemGroup>

If there are few appsettings files used for different environments, e.g. appsettings.development.json or appsettings.production.json etc. they are merged into one generated class. Merge is based on first prefix in filename - here is appsettings.

Now generated class can be used to retreive the configuration:

var appSettings = _configuration.Get<AppSettings>();

and should be earlier added to container:

static IHostBuilder CreateHostBuilder(string[] args)
{
    var configuration = new ConfigurationBuilder()
       .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
       .AddEnvironmentVariables()
       .Build();

    return Host.CreateDefaultBuilder(args)
        .ConfigureServices((_, services) =>
            services
            .Configure<AppSettings>(configuration)
            .AddTransient<INotesService, NotesService>());
}