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))
            {
            }
        }
    });
}