Oh that should not have happened, thank you for reporting this! I have logged an issue to fix NullRef exception.
The optional `drawAndEdit` parameter is to complete the task as soon as something is drawn. In the case of Polygon, after double-tap occurs and there's at least 3 vertices, it will be completed without going to edit mode or requiring Stop/Complete to be called.
Since you plan to complete the draw programmatically given your specific condition, you can alternatively use EditConfiguration to disable the edits you don't need, or
var config = new SketchEditConfiguration()
{
AllowVertexEditing = false,
AllowMove = false,
AllowRotate = false,
ResizeMode = SketchResizeMode.None
};
var geom = await MyMapView.SketchEditor.StartAsync(SketchCreationMode.Polygon, config);
you can change the symbols in the Style.
MyMapView.SketchEditor.Style.ShowNumbersForVertices = false;
MyMapView.SketchEditor.Style.SelectionColor = Color.Red;
MyMapView.SketchEditor.Style.SelectedVertexSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle.Circle, Color.Red, 1);
MyMapView.SketchEditor.Style.VertexSymbol = null;
MyMapView.SketchEditor.Style.MidVertexSymbol = null;
var geom = await MyMapView.SketchEditor.StartAsync(SketchCreationMode.Polygon);
We still need to fix the NullRef ex but meanwhile you have the option to use any of the above suggestions.