public void Delete( 
   MapMember mapMember,
   long oid
)

// Deletes a single feature from the specified feature layer using its ObjectID.
await QueuedTask.Run(() =>
      {
        var deleteFeatures = new EditOperation() { Name = "Delete single feature" };
        //Delete a row in a standalone table
        deleteFeatures.Delete(featureLayer, objectId);
        //Execute to execute the operation
        //Must be called within QueuedTask.Run
        if (!deleteFeatures.IsEmpty)
        { //Execute and ExecuteAsync will return true if the operation was successful and false if not
          var result = deleteFeatures.Execute();
          //or use async flavor
          //await deleteFeatures.ExecuteAsync();
        }
      });