public sealed class ServiceConnectionProperties : Connector 

{
  //Url examples for (federated) feature services
  //(by "ref" online):
  var url =
      @"https://sampleserver6.arcgisonline.com/arcgis/rest/services/LocalGovernment/Recreation/FeatureServer";
  //(federated by ref on portal)
  //https://portal.example.com/server/rest/services/FeatureServiceName/FeatureServer
  //(federated by value - Hosted - on portal)
  //https://portal.example.com/server/rest/services/Hosted/FeatureServiceName/FeatureServer

  await QueuedTask.Run(() =>
  {
    var uri = new Uri(url, UriKind.Absolute);
    using (var fs_db =
        new ArcGIS.Core.Data.Geodatabase(new ServiceConnectionProperties(uri)))
    {
      //Use the geodatabase
    }
  });
}

{
  await QueuedTask.Run(() =>
  {
    Uri nonFederatedServerURL = new Uri(
    "https://arcgis.server.example.com:6443/arcgis/rest/services/FeatureServiceName/FeatureServer");

    // Note that for non-federated ArcGIS Server hosted feature services,
    // the username and password have to be specified always.
    ServiceConnectionProperties nonFederatedArcGISServer =
          new ServiceConnectionProperties(nonFederatedServerURL)
          {
            User = "serverUser",
            Password = "serverPassword"
          };

    using (Geodatabase nonFederatedServerFeatureService =
      new Geodatabase(nonFederatedArcGISServer))
    {
      // Use the feature service geodatabase.
    }

    //Hosted (or published "by value")
    Uri federatedServerURL = new Uri(
      "http://federated.with.portal.example.com/server/rest/services/Hosted/FeatureServiceName/FeatureServer");
    //Published "by reference"
    //Uri federatedServerURL = new Uri(
    //"http://federated.with.portal.example.com/server/rest/services/FeatureServiceName/FeatureServer");

    // Note that for feature services hosted on ArcGIS Server federated with
    // ArcGIS Portal, the username and password cannot be specified through the API. 
    // Even if the username and password were specified, they will be disregarded.
    // Instead the Portal authorization has to be configured by adding the Portal to
    // ArcGIS Pro with the user with which the connection should be established.
    // To connect to a Portal from a CoreHost application, use the
    // ArcGIS.Core.SystemCore.ArcGISSignOn class to authenticate with the Portal.

    ServiceConnectionProperties federatedArcGISServer =
      new ServiceConnectionProperties(federatedServerURL);

    using (Geodatabase federatedServerFeatureService =
      new Geodatabase(federatedArcGISServer))
    {
      // Use the feature service geodatabase.
    }

    Uri arcgisOnlineURL = new Uri(
      "http://services1.arcgis.com/47GG2ga246DGaLwa/arcgis/rest/services/FeatureServiceName/FeatureServer");
    //or
    //https://sampleserver6.arcgisonline.com/arcgis/rest/services/LocalGovernment/Recreation/FeatureServer
    //etc

    // Similar to Federated Feature Services, note that for feature services
    // hosted on ArcGIS Online, the username and password cannot be specified through
    // the API. Even if the username and password were specified, they will be
    // disregarded. Instead the connection will be established based on the ArcGIS
    // Online user credentials used to login to ArcGIS Pro at startup.

    ServiceConnectionProperties arcGISOnline =
      new ServiceConnectionProperties(arcgisOnlineURL);

    using (Geodatabase arcGISOnlineFeatureService =
      new Geodatabase(arcGISOnline))
    {
      // Use the feature service geodatabase.
    }
  });

}

{
  await QueuedTask.Run(() =>
  {
    Layer selectedLayer = MapView.Active.GetSelectedLayers()[0];

    if (selectedLayer is FeatureLayer)
    {
      FeatureLayer featureLayer = selectedLayer as FeatureLayer;

      using (Table table = featureLayer.GetTable())
      using (Datastore datastore = table.GetDatastore())
      {
        ServiceConnectionProperties serviceConnectionProperties = datastore.GetConnector() as ServiceConnectionProperties;

        if (serviceConnectionProperties == null)
          return;

        Uri url = serviceConnectionProperties.URL;      // Will be the URL to the Feature Service.
        string user = serviceConnectionProperties.User;     // The username property will only be
                                                            // populated for feature service hosted
                                                            // on non-federated ArcGIS Server.
        string password = serviceConnectionProperties.Password; // Will always be empty.
      }
    }
  });
}