AppSettings values cannot read when using dependency injection

Question

first of all I am a very beginner with dependency injection. I am trying to read appsettings.json configuration values from one of my class

here is my code

private readonly IConfiguration _configuration;
public AdoExtract(IConfiguration configuration = null)
{
    _configuration = configuration;
}
public List<ApiAdoProject> ExtractAllWorkitems()
{
    List<ApiAdoProject> projects = new List<ApiAdoProject>();
    projects = GetAllProjects();
    return projects;
    //foreach (var prj in projects)
    //{
    //    string s = prj.name;
    //}
}

List<ApiAdoProject> GetAllProjects()
{
    Uri uri = new Uri("https://dev.azure.com/****");
    VssBasicCredential credentials =
        new VssBasicCredential("", _configuration["PAT"]);

    using (ProjectHttpClient projectHttpClient =
        new ProjectHttpClient(uri, credentials))
    {
        IEnumerable<TeamProjectReference> projects =
            projectHttpClient.GetProjects().Result;
    }
    return null;
}

When I run this _configuration["PAT"] returning null

Here is my appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*",
  "PAT": "mypat",
  "ClientId": "567567567567546",
  "ClientSecret": "",
  "ConnectionStrings": {
    "EpmoDb": "mycd"
  }
}

Here is my startup

public Startup(IConfiguration configuration)
{
    Configuration = configuration;
}

public IConfiguration Configuration { get; }

Code which use adocontroller

namespace EPMO_Toolset_API.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class AdoController : ControllerBase
    {
        private readonly IConfiguration _configuration;
        public AdoController(IConfiguration configuration = null)
        {
            _configuration = configuration;
        }
        // GET: api/<AdoController>
        [HttpGet]
        public List<ApiAdoProject> Get()
        {
            AdoExtract ado = new AdoExtract();
            return ado.ExtractAllWorkitems();
        }

Did I missed anything or what I did wrong

Show the code where you configure AdoExtract for DI, and the relevant parts of the code that use AdoExtract — Caius Jard
– Caius Jard, Commented Mar 22, 2021 at 7:44
Sorry the first code snippet is where I am using _configuration which is AdoExtract.cs — Sandeep Thomas
– Sandeep Thomas, Commented Mar 22, 2021 at 7:57
var result = _configuration["PAT"];,for me, this code worked well,you can test it in your controller.I think you have done nothing wrong, there may be a problem elsewhere — Yinqiu
– Yinqiu, Commented Mar 22, 2021 at 7:59
I mean show ConfiguresServices in startup (AdoExtract has to be registered), and also show the class that uses AdoExtract; how does an instance of AdoExtract come to be a thing that class can use? — Caius Jard
– Caius Jard, Commented Mar 22, 2021 at 8:11

Steven · Accepted Answer · 2021-03-22 10:16:21Z

2

You wouldn't do this:

AdoExtract ado = new AdoExtract();

Because that runs the AdoExtract constructor with a null IConfiguration, and it is AdoExtract that wants to use the configuration, so it can't be null

You would perhaps instead do something more like injecting the IAdoExtract into the controller:

public AdoController(IAdoExtract x)

And have registered the IAdoExtract to AdoExtract in your ConfigureServices, it means that the configured instance will be used because the DI creates the AdoExtract, it sees that it needs an IConfiguration and it knows how to provide it. If you create the AdoExtract yourself you're bypassing this and provding a null configuration instead

    public void ConfigureServices(IServiceCollection services)
    {
        ...
        // decide a suitable lifetime eg Transient/Scoped etc
        services.AddScoped<IAdoExtract, AdoExtract>();
    }

edited Mar 22, 2021 at 10:16

Steven

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answered Mar 22, 2021 at 8:20

Caius Jard

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2 Comments

Sandeep Thomas Over a year ago

It works great.. I have added this in my configureservices services.AddScoped<IAdoExtract, AdoExtract>(); It is working now. But AddScoped is correct. Or singleton? I am very unfamiliar with those.. :(

Caius Jard Over a year ago

Well, only you can know if a Singleton or Scoped etc will be useful but if it's doing database access I would probably make it scoped

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