using Bandwidth.Netx.Extra;

var appId = await client.Application.GetOrCreateAsync('My app', 'my.domain.com'); // It will return exisitng application Id or create it otherwise

var number = await client.PhoneNumber.GetOrCreateAsync(client.AvailableNumber, appId, 'Support', new LocalNumberQueryForOrder{AreaCode = "910"}); // It will reserve a linked to this app phone number and assign name to it. If number with such name already exists it returns it.

public class Startup
{
   public void ConfigureServices(IServiceCollection services)
   {
      // Register Banwidth API services. They are used by middleware too.
      services.AddBandwidth(new BandwidthAuthData
      {
        UserId = "userId",
        ApiToken = "apiToken",
        ApiSecret = "apiSecret"
      });
   }
   public void Configure(IApplicationBuilder app)
   {
      // Using a middleware
      app.UseBandwidth(new BandidthOptions
      {
        ApplicationName = "My App",
        PhoneNumber = new PhoneNumberOptions
        {
          LocalNumberQueryForOrder = new LocalNumberQueryForOrder // leave LocalNumberQueryForOrder with null to allocate toll free number
          {
            AreaCode = "910"
          }
        },
        CallCallback = async (eventData, context) // as alternative you can use CallCallbackDictionary to handle only specific events
        {
          // handle call events here (including sip events too)
          if(eventData.EventType == CallbackEventType.Answer && context.Items["PhoneNumber"] == eventData.To){
            Debug.WriteLine('Answered');
          }
        }
      });
   }
}

public class MyController: Controller
{
  public MyController(ICall call) // via Dependency Injection
  {

  }

  public IActionResult MyAction()
  {
    return Json(new {PhoneNumber = HttpContext.GetPhoneNumber()}); // using allocated phone number
  }
}