.Net accessing instantiated class members by string variable

Question

How can I access top-level class members using a string variable similar to how one is able to access .Net configuration values using a string variable.

// appsettings.json
{
    "ConfigKey":"SomeConfigValue"
}

class SomeTrivialClass {

    public SomeTrivialClass() {

         var configuration = new ConfigurationBuilder().Build();

         var someConfigKey = "ConfigKey";

         var someConfigValue = configuration[someConfigKey] 

         Console.WriteLine(someConfigValue);
    }
}

new SomeTrivialClass() // writes SomeConfigValue