Configuration Extensions

The project contains two utilities to solve some general problems. These are not a silver bullet and don't solve all your problems, but do your coding a little bit easier.

AutoBind

The package contains helpers to make your code a bit less verbose when you add a new configuration option class to your system.

Install the package:

Install-Package Contrib.Extensions.Configuration.AutoBind

Use AutoBind:

public class MyServerOptions
{
    // ...
}

// in the Startup.cs:
public void ConfigureServices(IServiceCollection services)
{
    // This call bind the MyServerOptions class to the configuration file section with the 'MyServerOptions' name
    services.AddOptions<MyServerOptions>().AutoBind();
}

You can customize the section name by adding a class-level read-only property or field to the class with the name 'SectionName' as follow:

public class MyServerOptions
{
    // You can use const string field
    public const string SectionName = "MyCoolOptions";
    // or 
    public static readonly string SectionName = "AnotherCoolOptions";
    // or
    public static string SectionName { get; }  = "CoolOptions";
}

If the class contains one of these fields or properties, AutoBind uses it. If not, it uses the class name.

VariablesSubstitution

The package allows you to expand environment variables in configuration files.

Basic usage

Install the package:

Install-Package Contrib.Extensions.Configuration.VariablesSubstitution

Define a configuration option class:

public class MyServerOptions
{
    public string TempFolder { get; set; }
    public string DataFiles { get; set; }
    // other options
    // ...
}

Bind the class to a configuration file section and configure it:

services.AddOptions<MyServerOptions>()
    .AutoBind()
    .SubstituteVariables(); // This call makes it happen

Now you can add a configuration section and use environment variables in your appsettings.json:

{
    "MyServerOptions": {
        "TempFolder": "%TEMP%/MyApp",
        "DataFiles": "%AppData%/MyApp/DataFiles"
    }
}

The substitution works for all nested options including any types of mutable lists and dictionaries. So, this will work too:

public class MyServerOptions
{
    public class SubOptions
    {
        public string Proxy { get; set; }
    }

    public string TempFolder { get; set; }
    public string DataFiles { get; set; }
    public string[] StringList { get; set; }
    public SubOptions SubOptions { get; set; }
    public List<SubOptions> SubOptionsList { get; set; }
    public Dictionary<string, string> DictionaryOfStrings { get; set; }
}

{
    "MyServerOptions": {
        "TempFolder": "%TEMP%/MyApp",
        "DataFiles": "%AppData%/MyApp/DataFiles",
        "StringList": [
            "value1",
            "%USER%"
        ],
        "SubOptions": {
            "Proxy": "%PROXY_ADDRESS%"
        },
        "SubOptionsList": [
            {
                "Proxy": "%PROXY_ADDRESS%",
            },
            {
                "Proxy": "%PROXY_ADDRESS%",
            }
        ],
        "DictionaryOfStrings": {
            "s1": "%TEMP%/s1",
            "s2": "%TEMP%/s2"
        }
    }
}

Customization

But what if you do want to use $TEMP or $(TEMP) instead of %TEMP%, or maybe don't want to use environment variables?

You can do it with two steps:

1. Implement the interface:

namespace Contrib.Extensions.Configuration.VariablesSubstitution
{
    public interface IVariablesSubstitution<T>
    {
        T Substitute(T value);
    }
}

2. Register the implementation in the DI-container BEFORE any call of SubstituteVariables:

// Register your implementation
services.AddSingleton<IVariablesSubstitution<string>, YourImplementation>();

services.AddOptions<MyServerOptions>()
    .AutoBind()
    .SubstituteVariables();

Versions

Date	Version	Description
2021-02-22	1.2.0	Support Dictionary<TKey, TValue> of strings and nested options
2020-08-13	1.1.0	Support lists of nested options and strings
2020-07-17	1.0.0	Initial release

Have fun!