SortingLayer allows you to set the render order of multiple sprites easily. There is always a default SortingLayer named "Default" which all sprites are added to initially. Added more SortingLayers to easily control the order of rendering of groups of sprites. Layers can be ordered before or after the default layer.
This is the unique id assigned to the layer. It is not an ordered running value and it should not be used to compare with other layers to determine the sorting order.
Returns the final sorting layer value. To determine the sorting order between the various sorting layers, use this method to retrieve the final sorting value and use CompareTo to determine the order.