如何使用c＃中的数据集从数据库中获取最近注册的数据

Question

如何使用c＃中的数据集从数据库中获取最近注册的数据？我想在两个给定日期之间获得最近的注册数据。

我的表在数据库中是这样的： Table in the database

我目前的代码是这样的：

public DataSet getRecentRegistrations(DateTime startMonth, DateTime endMonth, long setaCode)
{
    var query = (from _transaction in
    _entities.LevyTransactions
        join _seta in _entities.Setas on _transaction.SetaCode equals _seta.SetaCode
        join company_details in _entities.Organisations on _transaction.Refno equals company_details.Refno
        where(_transaction.TransactionDate >= startMonth || startMonth == null)
            && (_transaction.TransactionDate <= endMonth || endMonth == null)
            && (_transaction.SetaCode == setaCode || setaCode < 0)
        select new
        {
            SetaCode = _transaction.SetaCode,
            RefNo = company_details.Refno,
            TradingName = company_details.TradingName,              
            Seta = _transaction.SetaCode+" - "+_seta.Description,
            SetaLevy = _transaction.SetaLevy,
            SetaInterest = _transaction.SetaInterest,
            SetaAdmin = _transaction.SetaAdmin,
            SetaPenalty = _transaction.SetaPenalty,
            TotalSetaCollected = _transaction.TotalSetaCollected
        });

    DataSet ds = new DataSet();
    ds.Tables.Add(query.CopyToDataTable());ds.Tables[0].TableName = "Table1";  
    ds.Tables.Add(headerTable("Transaction Month From : "
        + HelperService.formatDate("yyyy-MM-dd", startMonth) + " To :"
        + HelperService.formatDate("yyyy-MM-dd", endMonth),"Recently Registered Companies")); 
    ds.Tables[1].TableName ="Table2";
    var setaRows = (from DataRow dRow in ds.Tables[0].Rows
        select new { SetaCode = dRow["SetaCode"], Seta = dRow["Seta"]}).Distinct();      
    ds.Tables.Add(setaRows.CopyToDataTable()); ds.Tables[2].TableName = "Table3";

    return ds;
}

输出应该如下图所示。

最近注册日期： 2014-04-01 -2014-05-01

Output