复合子条件查询

if (input.ApprovalStatus != null)
{
    var whereStatus = LinqHelper.False<data_paichan>();

    if (input.ApprovalStatus.Contains("Y"))
    {
        whereStatus = whereStatus.Or(w => w.approval_status == "Y");
    }
    if (input.ApprovalStatus.Contains("N"))
    {
        whereStatus = whereStatus.Or(w => w.approval_status != "Y");
    }

    queryEntity = queryEntity.Where(whereStatus);
}