Combined primary keys with petapoco

Questions
1

The following create a primary key for the first column only. Any suggestions please to resolve the issue?

[TableName(“tsLcValues”)]
[ExplicitColumns]
[PrimaryKey(“LcTableID,LcResourceID,CultureISOCode,RowID”, autoIncrement = false)]
public class tsLcValue
{
public tsLcValue() { }

    [Column("LcTableID")]
    [PrimaryKeyColumn(AutoIncrement = false)]
    public int LcTableID { get; set; }

    [Column("LcResourceID")]
    [PrimaryKeyColumn(AutoIncrement = false)]
    public int LcResourceID { get; set; }

    [Column("CultureISOCode")]
    [Length(5)]
    [Constraint(Default = "")]
    [PrimaryKeyColumn(AutoIncrement = false)]
    public string CultureISOCode { get; set; }

    [Column("RowID")]
    [PrimaryKeyColumn(AutoIncrement = false)]
    public int RowID { get; set; }

    [Column("ResourceValue")]
    [Constraint(Default = "")]
    public string ResourceValue { get; set; }
}
This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/59672-combined-primary-keys-with-petapoco