Using Appsettings In Console Applications - Taken from Seeman

appsettings.json

{
  "messageWriter":
    "Ploeh.Samples.HelloDI.Console.ConsoleMessageWriter, HelloDI.Console"
}

Main.cs

IConfigurationRoot configuration = new ConfigurationBuilder()
    .SetBasePath(Directory.GetCurrentDirectory())
    .AddJsonFile("appsettings.json")
    .Build();

string typeName = configuration["messageWriter"];
Type type = Type.GetType(typeName, throwOnError: true);

IMessageWriter writer = (IMessageWriter)Activator.CreateInstance(type);