Injectable Settings for .NET

This is a small library for fetching configuration settings with your favourite dependency injection container. If your class depends on values stored in App.config or Web.config, you'll want a thin abstraction layer to allow for easier testing without writing a lot of repetitive code.

InjectableSettings is a thin conventions-based wrapper for AppSettings key value pairs that allows for them to be injected into your class with NInject, AutoFac, Unity, Castle Windsor, or whatever IoC framework you like.

Usage

You simply derive a type from ConfigurationSetting. As long as you make sure the name of your class ends with ConfigurationSetting, things will work:

public class ExampleConfigurationSetting : ConfigurationSetting {}

Now put an app setting in App.config as follows:

<appSettings>
   <add key="Example" value="foo" />
</appSettings>

Now, when you need access to the example setting, all you need to do is new up an ExampleConfigurationSetting, or have it handed to you by the DI container:

public class ExampleThatNeedsAnExampleSetting
{
  private readonly string example;

  // Constructor injection used here:
  public ExampleThatNeedsAnExampleSetting(ExampleConfigurationSetting example)
  {
    this.example = example.Value;
  }

  // Now go use your foo!
}

Simple unit testing

Let's unit test the example used above. We can simply new up the configuration setting with the exact value we want, no need for complicated mocking or stubbing or other pre-wiring:

[Test]
public void ExampleWorksWithBar()
{
  // Arrange
  var example = new ExampleConfigurationSetting { Value = "bar" };
  var sut = new ExampleThatNeedsExampleSetting(example);
  
  // Act & assert left as an exercise to the reader.
}

Default values

By default, if no other default is specified, the configuration setting will have a null value when nothing is specified in App.config. You can supply a default value as follows:

public class ExampleConfigurationSetting : ConfigurationSetting
{
  public ExampleConfigurationSetting : base("bar") {}
}

FAQ

A Few Anticipated Questions:

Can I fetch connection strings and other stuff from App.config too?

No, I didn't need that. I accept pull requests though.
These are all strings, I want to read integers, Guids, Urls (mutatis mutandis) instead.

You can do that. The default is for the settings to work with strings, but if you derive your FooConfigurationSetting from ConfigurationSetting<T> it will return values of type T.
I want my keys to be 'namespaced', as such:
```
  <add key="Redis.Server" value="redis1.example.org" />
  <add key="Redis.Password" value="password" />
  <add key="Redis.AppName" value="MyApp.Staging" />
```
You can do that by nesting your settings in a class with a name that ends with Settings. In this case, you make a class named RedisSettings and put your ConfigurationSettings for Server, Password and AppName nested in that class.

As with all intended features, there is an example of this in the unit tests (see TestSettingsGroup.cs).
My settings are not in Web.config or App.config, they are some place else. Do you support that?

I have no plans for that at the moment, as it would complicate things.

Thanks for reading all the way up to here.

frankgeerlings/InjectableSettings

Injectable Settings for .NET

Usage

Simple unit testing

Default values

FAQ