If I share a layer from ArcMap as Geodatabase, How can I make it editable using ArcGIS Runtime in .NET (I have basic license and I only need to be able to edit it offline)?
Creating geodatabases using Desktop workflow creates read-only geodatabases, if you want to edit a geodatabase, you need to create it through FeatureLayer (you can create sync enabled geodatabase before providing it to the application if needed too, this is called "pre-planned" workflow).
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Sync offline edits—ArcGIS Runtime SDK for .NET | ArcGIS for Developers