private Task ApplyLabelFeatureLayerAsync() { return(QueuedTask.Run(() => { //Get the layer's definition var lyrDefn = SelectedLayer.GetDefinition() as CIMFeatureLayer; //Get the label classes - we need the first one var listLabelClasses = lyrDefn.LabelClasses.ToList(); var theLabelClass = listLabelClasses.FirstOrDefault(); //Place all labels horizontally theLabelClass.StandardLabelPlacementProperties.LineLabelPosition.Horizontal = true; //Set the label classes' symbol to the custom text symbol theLabelClass.TextSymbol.Symbol = SelectedTextStyle.Symbol; lyrDefn.LabelClasses = listLabelClasses.ToArray(); //Set the labelClasses back SelectedLayer.SetDefinition(lyrDefn); //set the label's visiblity if (IsLabelVisible) { (SelectedLayer as FeatureLayer).SetLabelVisibility(true); } })); }