public string WorkspaceConnectionString {get; set;}

CIMStandardDataConnection cIMStandardDataConnection = new CIMStandardDataConnection()
{
  WorkspaceConnectionString = @"SWAPXY=TRUE;SWAPXYFILTER=FALSE;URL=http://sampleserver6.arcgisonline.com/arcgis/services/SampleWorldCities/MapServer/WFSServer;VERSION=2.0.0",
  WorkspaceFactory = WorkspaceFactory.WFS,
  Dataset = "Continent",
  DatasetType = esriDatasetType.esriDTFeatureClass
};

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

CIMStandardDataConnection dataConnection = dataConnectionLayer.GetDataConnection() as CIMStandardDataConnection;
dataConnection.WorkspaceConnectionString = newConnectionString;
dataConnectionLayer.SetDataConnection(dataConnection);