var builder = new ConfigurationBuilder();

​

// add static values

builder.AddInMemoryCollection(new Dictionary<string, string>

{

    { "MyKey", "MyValue" },

});

​

// add values from a json file

builder.AddJsonFile("appsettings.json");

​

// create the IConfigurationRoot instance

IConfigurationRoot config = builder.Build();

​

string value = config["MyKey"]; // get a value

IConfigurationSection section = config.GetSection("SubSection"); //get a section