I was surprized to find the FeatureCollectionLayer FullExtent is the same as the first FeatureLayer FullExtent. I was expecting that FeatureCollectionLayer FullExtent to be the merged FullExtent of FeatureLayers. Can you make it as a merged FullExtent?
Here is what I observe.
FeatureCollectionLayer:
+ FullExtent {Envelope[XMin=-13622705.208700001, YMin=4525742.4318, XMax=-13621444.297, YMax=4527008.828199998, Wkid=102100]} Esri.ArcGISRuntime.Geometry.Envelope
FeatureLayers:
+ FullExtent {Envelope[XMin=-13622705.208700001, YMin=4525742.4318, XMax=-13621444.297, YMax=4527008.828199998, Wkid=102100]} Esri.ArcGISRuntime.Geometry.Envelope
+ FullExtent {Envelope[XMin=-13623596.731800001, YMin=4524476.341600001, XMax=-13621444.297, YMax=4525742.508199997, Wkid=102100]} Esri.ArcGISRuntime.Geometry.Envelope
+ FullExtent {Envelope[XMin=-13623966.120299999, YMin=4524847.139200002, XMax=-13622705.208700001, YMax=4527008.828199998, Wkid=102100]} Esri.ArcGISRuntime.Geometry.Envelope
