.Resx file is empty when using it in .cs file - asp.net-core

Question

I am trying to read data from .resx file. It works fine in views, but having trouble when using it in .cs.
I am getting this runtime error:
Object reference not set to an instance of an object
MailComposer.cs
IStringLocalizer<SharedResources> SharedLocalizer;
public void SendActivityCreated (Activity entity) {
var path = Path.Combine (environment.ContentRootPath, "wwwroot", "mail_templates", "activity_created", "index.html");
var template = File.ReadAllText (path);
template = template.Replace ("##ID##", entity.ID.ToString ());
var x = SharedLocalizer["NewActivity"]; // Getting "Object reference not set to an instance of an object" here
var title = $"Platform.Ge - {x} #{entity.ID}";
var responsibleEmail = template.Replace ("##USER##", entity.Responsible.Name);
emailSender.SendEmailAsync (entity.Responsible.Email, title, responsibleEmail);
}
Startup.cs
services.Configure<RequestLocalizationOptions> (opts => {
var supportedCultures = new [] {
new CultureInfo ("en"),
new CultureInfo ("ka"),
new CultureInfo ("ru")
};
opts.DefaultRequestCulture = new RequestCulture ("ka");
// Formatting numbers, dates, etc.
opts.SupportedCultures = supportedCultures;
// UI strings that we have localized.
opts.SupportedUICultures = supportedCultures;
});
I have SharedResources.ka.resx and SharedResources.en.resx files. How do I get data from these two files in SharedLocalizer instance of MailComposer.cs?

Answer 1

Solution 1 :
Inject SharedResources in MailComposer.cs :
IStringLocalizer<SharedResource> SharedLocalizer;
public MailComposer(IStringLocalizer<SharedResource> _SharedLocalizer)
{
SharedLocalizer = _SharedLocalizer;
}
Add below line in Startup.cs :
services.AddScoped<MailComposer>();
Inject MailComposer in the place where you want to call the SendActivityCreated function ：
private readonly MailComposer _mailComposer;
public HomeController(MailComposer mailComposer){
_mailComposer = mailComposer;
}
And use like :
_mailComposer.SendActivityCreated(entity);
Solution 2 :
Inject SharedResources in MailComposer.cs :
IStringLocalizer<SharedResource> SharedLocalizer;
public MailComposer(IStringLocalizer<SharedResource> _SharedLocalizer)
{
SharedLocalizer = _SharedLocalizer;
}
Inject IStringLocalizer<SharedResource> in the place where you want to call the SendActivityCreated function ：
private readonly IStringLocalizer<SharedResource> _localizer;
public HomeController(IStringLocalizer<SharedResource> localizer){
_localizer = localizer;
}
And use like :
MailComposer a = new MailComposer(_localizer);
a.SendActivityCreated(entity);