how to get value from appsettings.json

问题:

public class Bar
{
    public static readonly string Foo = ConfigurationManager.AppSettings["Foo"];
}

In the .NET Framework 4.x, I can use the ConfigurationManager.AppSettings ["Foo"] to get Foo in Webconfig,and then I can easily get the value of Foo through Bar.Foo

But in .Net core, I mustto inject options, And can not get the value of Foothrough Bar.Foo

Is there a method, which can be directly through the Bar.Foo to get the value of Foo?

回答1:

So there are really two ways to go about this.

Option 1 : Options Class

You have an appsettings.json file :

{
  "myConfiguration": {
    "myProperty": true 
  }
}

You create a Configuration POCO like so :

public class MyConfiguration
{
    public bool MyProperty { get; set; }
}

In your startup.cs you have something in your ConfigureServices that registers the configuration :

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

Then in your controller/service you inject in the IOptions and it's useable.

public class ValuesController : Controller
{
    private readonly MyConfiguration _myConfiguration;

    public ValuesController(IOptions<MyConfiguration> myConfiguration)
    {
        _myConfiguration = myConfiguration.Value;
    }
}

Personally I don't like using IOptions because I think it drags along some extra junk that I don't really want, but you can do cool things like hot swapping and stuff with it.

Option 2 : Configuration POCO

It's mostly the same but in your Configure Services method you instead bind to a singleton of your POCO.

public void ConfigureServices(IServiceCollection services)
{
    //services.Configure<MyConfiguration>(Configuration.GetSection("myConfiguration"));
    services.AddSingleton(Configuration.GetSection("myConfiguration").Get<MyConfiguration>());
}

And then you can just inject the POCO directly :

public class ValuesController : Controller
{
    private readonly MyConfiguration _myConfiguration;

    public ValuesController(MyConfiguration myConfiguration)
    {
        _myConfiguration = myConfiguration;
    }
}

A little simplistic because you should probably use an interface to make unit testing a bit easier but you get the idea.

Mostly taken from here : http://dotnetcoretutorials.com/2016/12/26/custom-configuration-sections-asp-net-core/

回答2:

You can also use the configuration directly. Your settings are injected so you can get to them with DI...

private readonly IConfiguration _configuration;

public MyClass(IConfiguration configuration)
{
    _configuration = configuration;
}

and then you can read your settings...

In this case I'm getting a collection back...

var myList = _configuration.GetSection("MyList").Get<List<string>>();

回答3:

The solutions on top are time consuming and not straightforward, this is the best effective way to do it, no setup needed on startup or anything. It's like using the good ol Configuration.Manager.AppSettings["setting"]

First create a class like "Credential":

public class Credential
  {
      public string Username {get;set}
      public string Password {get;set;}
  }

Now that's setup let put the IConfiguration on your constructor like so:

    private IConfiguration _configuration;
    public ValuesController(IConfiguration iconfig)
    {
        _configuration = iconfig;
    }

Then you're ready to call it!

    Credential c = new Credential();
    c.UserName = _configuration.GetValue<string>("Credential:username");
    c.Password = _configuration.GetValue<string>("Credential:password");

Assuming your appsettings.json looks like this:

"Credential": {
    "username": "myuser",
    "password": "mypassword"
  }

Hope this helps somebody.