How can I use DI for 3'rd party static class in Dot Net Core?

Question

Someone in our company wrote ( by mistake, a long time ago ) this static class, being served from Nuget : (I can't edit it)

public static class MailService
 {

    public static void SendEmail(string recipients, string subject, string msg  )
    {
        SendEmail(recipients, subject,  msg);
    }
...
}

I already know it's bad. But let's continue.
I want to use this class via DI in my asp.net core project.
Problem is that I can't use this (because static can't be new'ed):

  services.AddSingleton<MailService>();

Question:

Is there still a way to make MailService (or any wrapper for it ) Injectable?

Answer 1

It's as simple as this:

public interface IMailService {
    void SendEmail(string recipients, string subject, string msg);
}

public class MailServiceWrapper : IMailService {
    public void SendEmail(string recipients, string subject, string msg) {
        MailService.SendEmail(recipients, subject, msg);
    }
}

And in the Startup class:

services.AddSingleton<IMailService, MailServiceWrapper>();