I found the old thread related to this but it was using the old version of arcgis runtime. Is there a way I can use this service https://traffic.arcgis.com/arcgis/rest/services/World/Traffic/MapServer in the .NET app with the latest control?
I have created a webmap using the traffic.arcgis.com service, which is publicly shared. Using one of our existing sample, Security --> Authenticate with oAuth, and replacing the webmap with the existing one, you should be able to see the traffic map in Runtime application. You just need to enter the AGOL credential. This is one of ways to access the secured AGOL layer.
The webmap id is : 264678dc8f274a0c9dd157a08160bff7
Hope that helps.