ASP.NET Core Expose Config to DI Injected Service

问题

I have a ASP.NET Core WebAPI project and I am trying to add configuration to my IEmailServicethat I am injecting through DI like this:

services.AddTransient<IEmailSender, AuthMessageSender>();

How can instances of AuthMessageSender get to settings in the config file?

回答1:

You should use the options pattern with strongly typed configuration:

Create your EmailSettings strongly typed configuration class:

public class EmailSettings  
{
    public string HostName { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
}

Update your appsettings.json to include a configuration section that maps to your EmailSettings configuration class:

{
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
    }
  },
  "EmailSettings": {
    "HostName": "myhost.com",
    "Username": "me",
    "Password": "mysupersecretpassword",
  }
}

In the ConfigureServices call of your Startup class, bind appsettings.json to your config class

public void ConfigureServices(IServiceCollection services)  
{
    services.Configure<MySettings>(
          options => Configuration.GetSection("EmailSettings").Bind(options));
}

In your AuthMessageSender class, inject an instance of IOptions<EmailSettings> into the constructor

public class AuthMessageSender
{
    private readonly EmailSettings _settings;
    public AuthMessageSender(IOptions<EmailSettings> emailSettings)
    {
       _settings = emailSettings.Value;
      // _settings.HostName == "myhost.com";
    }
}

Note that in step 3, you can also use

public void ConfigureServices(IServiceCollection services)  
{
    services.Configure<MySettings>(Configuration.GetSection("EmailSettings"));
}

If you add a reference to Microsoft.Extensions.Options.ConfigurationExtensions in project.json:

{
  "dependencies": {
     "Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0"
  }
}

回答2:

The recommended pattern is to read the specific config entries you need at startup and store them in an Options instance in DI, and inject that specific options type into your other components.

来源：https://stackoverflow.com/questions/38108400/asp-net-core-expose-config-to-di-injected-service

标签

configuration

asp.net-core