将从 IOption 解析的设置注入 .NET Core 中的附加类

Question

How to inject Settings created from IOptions value to call some class method?

I have MailAppSettings class and MailSender: IMailSender . Both are in different .NET projects.

Values into MailAppSettings are loaded using IOptions pattern in .NET Core. Values are loaded from appsettings.json configuration. For DI we use AutoFac, so it looks like this:

 serviceCollection.AddOptions();
 serviceCollection.Configure<MailAppSettings>(config.GetSection("MailAppSettings"));

And later then we access mailSettings like this:

 public class CustomerSender:ICustomerSender
   {
        private readonly MailSettings _mailSettings;
        private readonly IMailSender _mailSender;

        public MyCustomerSender(IOptions<MailSettings> mailSettings, IMailSender mailSender)
        {
            _mailSettings = mailSettings.Value;
            _mailSender = mailSender;
        }

        public SomeCustomMethod1() {
        // use of mailsettings
            var recipient = mailSettings.Recipient1;
            var body = BuildSomeBody();
            var subject = mailSettings.Subject1;

            // mail sending
            _mailSender.Send(recipient, body, subject);
         }

mailSender is the class that sits in separate namespace and is called from different places in different projects.

    public class MailSender: IMailSender
    {
        private readonly IMailSenderSettings _mailSenderSettings;

        public MailSender(IMailSenderSettings confg) ///!!! here we need to inject those settings
        {
            _mailSenderSettings= confg;
        }
        ...

Here, you see that mailSender needs IMailSenderSettings to be injected. MailAppSettings implements this interface (but also contains additional properties).

My question is- how to inject MailAppSettings into IMailSenderSettings ? If I just register type like this:

containerBuilder.RegisterType<MailAppSettings>()
               .As<IMailSenderSettings>()
               .SingleInstance();

it won't work, values of injected IMailSenderSettings would be null.

IMailSenderSettings , as well as, MailAppSettings contains recipient , smtp host, password , user , but MailAppSettings also contains additional properties not needed for IMailSenderSettings

Answer 1

You will need to create IMailSenderSettings derived class that depends on MailSettings

public class MyMailSenderSettings: IMailSenderSettings {
    private readonly MailSettings mailSettings;

    public MyMailSenderSettings(IOptions<MailSettings> options) {
        this.mailSettings = options.Value;
    }

    public string SomeProperty => mailSettings.SomeMatchingProperty;

    //... other members mapped from settings 
}

so that the desired members can be mapped in the composition root.

From there it is only a matter of registering the implementation so that the DI container can handle the rest.

//...

serviceCollection.AddOptions();
serviceCollection.Configure<MailAppSettings>(config.GetSection("MailAppSettings"));

serviceCollection.AddSingleton<IMailSenderSettings, MyMailSenderSettings>()

//...