I have encountered an interesting bug in SL API: If a Feature Layer (from a Feature Service) is configured in ArcGIS server without Delete capability, calling Update() on that feature layer throws a ValidationException indicating that you are not allowed to delete features! I was trying to do filtering on a layer which does not have DELETE capability (I can't post the layer url here but you could try this ESRI's sample to reproduce: http://sampleserver6.arcgisonline.com/arcgis/rest/services/PoolPermits/FeatureServer/1). I was setting Where to a filter string and called Update immediately after that and boom I got hit by a ValidationException. I first thought it was because of the Where clause but even after removing the line that sets the Where clause and calling just Update I got the same error. I tried turning on and off DisableClientCaching, turning on and off ValidateEdits,..., nothing worked. I hope the bug gets fixed soon.
