Dot net core configuration setup

dotnetconfig.md

How to use config in dot net core

This env variable determines which appsettings.json file is used

name	value
ASPNETCORE_ENVIRONMENT	Development

If set to Development, it will use the values from appsettings.Development.json

If set to Production, it will use the values from appsettings.json

If set to Foo, it will use the values from appsettings.Foo.json

Example appsettings.json format

{
    "Config": {
        "ApplicationName": "MyApp",
        "Version": "10"
    }
}

If you set env variables in your system level environment variables, use this format (using colons):

name	value
Config:ApplicationName	AppName2
Config:Version	13

Note: You will need to restart Visual Studio when you add a new environment variable in order for it to be recognized

Note: Other environments (linux, mac) use _ and __ to show heirarchy

ASPNETCORE_My__Settings =

{
    "my": {
        "settings": "..."
    }
}

Untyped retrieval example

{
  "AppSettings": {
        "token": "1234"
    }
}

 var token = Configuration.GetSection("AppSettings:token");

More advanced

 "Serilog": {
        "WriteTo": [
            {
                "Name": "File",
                "Args": { "path": "%TEMP%\\Logs\\serilog-configuration-sample.txt" }
            }
        ]
    }

1. You need to use the index in the environment variable for arrays

name	value
Serilog:WriteTo:0:Args:path	%TEMP%\\customPath

Using Secrets

Anything that is sensitive (connection string passwords, api keys) should be kept in secrets.

Right click the project in Visual Studio and select Manage User Secrets

This creates a node in the csproj file called:

<PropertyGroup>
    <UserSecretsId>[guid]</UserSecretsId>
  </PropertyGroup>

The secrets file is kept here:

C:\Users\[Username]\AppData\Roaming\Microsoft\UserSecrets\[guid]

You would write the secrets in flattened form to overwrite the appsettings values:

{
    "Serilog:WriteTo:1:Args:splunkHost": "[your url]",
    "Serilog:WriteTo:1:Args:eventCollectorToken": "[your apiKey]"
}

Access the secret

if (env.IsDevelopment())
    {
        builder.AddUserSecrets<Startup>();
    }

public void ConfigureServices(IServiceCollection services)
    {
        _moviesApiKey = Configuration["Movies:ServiceApiKey"];
    }

Typed config in DotNetCore

Create a Config model

  public class Config
    {
        public string ApplicationName { get; set; }
        public int Version { get; set; }
    }

In Startup.cs

   public Startup(IHostingEnvironment env, IConfiguration configuration)
    {
        Configuration = configuration;
    }
 public void ConfigureServices(IServiceCollection services)
    {
        services.Configure<Config>(Configuration.GetSection("Config"));
        // Can access secrets also
        // services.Configure<Models.Serilog>(Configuration.GetSection("Serilog"));
    }

In Controllers

using Microsoft.Extensions.Options;

public class LogController : Controller
    {

        private readonly IOptions<Config> _config;
        public LogController( IOptions<Config> config)
        {
            _config = config;
        }

        [HttpGet]
        public IEnumerable<string> Get()
        {
            Console.WriteLine(_config.Value.ApplicationName);
            return;
        }
    }