SharedStringLocalizer class implements finding of resources in a shared project instead of domestic project (where type T is located).
Current implementation implies that resource will be searched in a shared project (Shared.Localization.Resources) in Resources folder and in a subfolder wich relates to type namespace.
For example, if we deal with HomeController class which has Shared.Localization.Main.Controllers namespace, resources for it will be searched in Resources\Main\Controllers\HomeController\HomeController.{locale}.resx file where locale refers to current culture locale name (en, de, ru, etc).