Compile Time

Run Time

  <appSettings>
    <add key="webpages:Version" value="3.0.0.0" />
    <add key="webpages:Enabled" value="false" />
    <add key="ClientValidationEnabled" value="true" />
    <add key="UnobtrusiveJavaScriptEnabled" value="true" />
    <add key="Greeting" value="Hello, Everyone!" />
    <add key="CurrentMajorDotNetVersion" value="6" />
  </appSettings>
  <system.web>
    <compilation debug="true" targetFramework="4.7.2" />
    <httpRuntime targetFramework="4.7.2" />
  </system.web>

<configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform">
  <connectionStrings>
    <add name="MyDB"
      connectionString="Data Source=ReleaseSQLServer..."
      xdt:Transform="SetAttributes" xdt:Locator="Match(name)"/>
  </connectionStrings>

  private string greeting = "";
  private int majorDotNetVersion = 0;
  public HomeController()
  {
      greeting = ConfigurationManager.AppSettings["Greeting"];
      string ver = ConfigurationManager.AppSettings["CurrentMajorDotNetVersion"]
      majorDotNetVersion = Int32.Parse(ver);
  }

{
    "Settings": {
        "KeyOne": 1,
        "KeyTwo": true,
        "KeyThree": {
            "Message": "Oh, that's nice...",
            "SupportedVersions": {
                "v1": "1.0.0",
                "v3": "3.0.7"
            }
        }
    }
}

public sealed class Settings
{
    public required int KeyOne { get; set; }
    public required bool KeyTwo { get; set; }
    public required NestedSettings KeyThree { get; set; };
}
public sealed class NestedSettings
{
    public required string Message { get; set; };
}

IConfigurationRoot config = new ConfigurationBuilder()
    .AddJsonFile("appsettings.json")
    .Build();
    
Settings? settings = 
  config.GetRequiredSection("Settings")
    .Get<Settings>();

{
  "Parent": {
    "FavoriteNumber": 7,
    "Child": {
      "Name": "Example",
      "GrandChild": {
        "Age": 3
      }
    }
  }
}

{
  "Parent:FavoriteNumber": 7,
  "Parent:Child:Name": "Example",
  "Parent:Child:GrandChild:Age": 3
}

File-based

• JSON
• XML
• INI
• Key-per-file

Others

• Environment variables
• Command-line
• In-Memory
• User Secrets
• Azure Key Vault
• Azure App Configuration

• Typically used to override settings found in appsettings.json or user secrets
• the : delimiter doesn't work for Hierarchical data on all platforms
• the __ delimiter is used instead of :

public class TransientFaultHandlingOptions
{
    public bool Enabled { get; set; }
    public TimeSpan AutoRetryDelay { get; set; }
}

set SecretKey="Secret key from environment"
set TransientFaultHandlingOptions__Enabled="true"
set TransientFaultHandlingOptions__AutoRetryDelay="00:00:13"

• There are built-in prefixes, like
  • ASPNETCORE_ for ASP.NET Core
  • DOTNET_ for .NET Core
• You can provide your own prefix

builder.Configuration.AddEnvironmentVariables(
  prefix: "MyCustomPrefix_");

set MyCustomPrefix_MyKey="My key with MyCustomPrefix_"
set MyCustomPrefix_Position__Title=Editor_with_custom
set MyCustomPrefix_Position__Name=Environment
dotnet run

Interface Segregation Principle (ISP): Scenarios (classes) that depend on configuration settings depend only on the configuration settings that they use.

Separation of Concerns : Settings for different parts of the app aren't dependent or coupled to one another.

• Must be non-abstract with a public parameterless constructor
• Contain public read-write properties to bind (fields are not bound)

public class FileOptions
{
    public string FileExtension { get; set; } ="";
    public string OutputDir { get; set; } ="";
    public string TemplateFile { get; set; } ="";
}

Resources

GitHub Repo

• https://github.com/codebytes/dotnet-configuration-in-depth

Docs

• .NET Configuration Docs

Contact

Chris Ayers

BlueSky: @chris-ayers.com
LinkedIn: - chris-l-ayers
Blog: https://chris-ayers.com/
GitHub: Codebytes
Mastodon: @Chrisayers@hachyderm.io
Twitter: @Chris_L_Ayers