public enum SelectionOption : System.Enum, System.IComparable, System.IConvertible, System.IFormattable, System.ISpanFormattable  

public async Task SelectingRowsFromATable()
{
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
    using (Table enterpriseTable = geodatabase.OpenDataset<Table>("LocalGovernment.GDB.piCIPCost"))
    {
      QueryFilter anotherQueryFilter = new QueryFilter { WhereClause = "FLOOR = 1 AND WING = 'E'" };

      // For Selecting all matching entries.
      using (Selection anotherSelection = enterpriseTable.Select(anotherQueryFilter, SelectionType.ObjectID, SelectionOption.Normal))
      {
      }

      // This can be used to get one record which matches the criteria. No assumptions can be made about which record satisfying the criteria is selected.
      using (Selection onlyOneSelection = enterpriseTable.Select(anotherQueryFilter, SelectionType.ObjectID, SelectionOption.OnlyOne))
      {
      }

      // This can be used to obtain a empty selction which can be used as a container to combine results from different selections.
      using (Selection emptySelection = enterpriseTable.Select(anotherQueryFilter, SelectionType.ObjectID, SelectionOption.Empty))
      {
      }

      // If you want to select all the records in a table.
      using (Selection allRecordSelection = enterpriseTable.Select(null, SelectionType.ObjectID, SelectionOption.Normal))
      {
      }
    }
  });
}

public async Task SelectingFeaturesFromAFeatureClass()
{
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    using (Geodatabase geodatabase = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde"))))
    using (FeatureClass enterpriseFeatureClass = geodatabase.OpenDataset<FeatureClass>("LocalGovernment.GDB.FacilitySite"))
    {
      List<Coordinate2D> newCoordinates = new List<Coordinate2D>
      {
        new Coordinate2D(1021570, 1880583),
        new Coordinate2D(1028730, 1880994),
        new Coordinate2D(1029718, 1875644),
        new Coordinate2D(1021405, 1875397)
      };

      SpatialQueryFilter spatialFilter = new SpatialQueryFilter
      {
        WhereClause = "FCODE = 'Park'",
        FilterGeometry = new PolygonBuilderEx(newCoordinates).ToGeometry(),
        SpatialRelationship = SpatialRelationship.Crosses
      };

      // For Selecting all matching entries.
      using (Selection anotherSelection = enterpriseFeatureClass.Select(spatialFilter, SelectionType.ObjectID, SelectionOption.Normal))
      {
      }

      // This can be used to get one record which matches the criteria. No assumptions can be made about which record satisfying the 
      // criteria is selected.
      using (Selection onlyOneSelection = enterpriseFeatureClass.Select(spatialFilter, SelectionType.ObjectID, SelectionOption.OnlyOne))
      {
      }

      // This can be used to obtain a empty selction which can be used as a container to combine results from different selections.
      using (Selection emptySelection = enterpriseFeatureClass.Select(spatialFilter, SelectionType.ObjectID, SelectionOption.Empty))
      {
      }

      // If you want to select all the records in a table.
      using (Selection allRecordSelection = enterpriseFeatureClass.Select(null, SelectionType.ObjectID, SelectionOption.Normal))
      {
      }
    }
  });
}