public class CIMWMSServiceConnection : CIMServiceConnection, System.ComponentModel.INotifyPropertyChanged, System.Xml.Serialization.IXmlSerializable  

// Create a connection to the WMS server
var serverConnection = new CIMInternetServerConnection { URL = "URL of the WMS service" };
var connection = new CIMWMSServiceConnection { ServerConnection = serverConnection };

// Add a new layer to the map
var layerParams = new LayerCreationParams(connection);
await QueuedTask.Run(() =>
{
  var layer = LayerFactory.Instance.CreateLayer<FeatureLayer>(layerParams, MapView.Active.Map);
});