c# - linq中的日期时间

Question

所以我试图从脚本任务中的表中获取最新记录。错误出现在 Linq 查询中，如下所示:

“无法将表达式‘Table(SSASLogging).Select(r=>r.TimeStamp).Max()’转换为 SQL 并且无法将其视为本地表达式。”

问题出在 DateTime 数据类型上，但我需要 DateTime 将其提供给我的 SSIS 变量。我知道这可以在执行 SQL 任务中轻松完成，但我现在已经放弃太远了!我知道 DateTime 有一些 LinqToSQL 方法，但它们只是为了比较，我不确定如何在此处应用它们。

    public DateTime getLatest()
    {
        DateTime result = new DateTime();

        //temp dummy/defaul date is two days ago
        result = DateTime.Now.AddDays(-2);

        try
        {
            //get the data connection string from the connection manager
            RW = (string)Dts.Connections["ReportingWarehouse"].ConnectionString;

            //Remove the Provider, Auto Translate, and Application
            //as it is not a parameter for the DataContext constructor
            RW = RW.Remove(RW.IndexOf("Provider=SQLNCLI10.1;"), "Provider=SQLNCLI10.1;".Length);
            RW = RW.Remove(RW.IndexOf("Auto Translate=False;"), "Provider=SQLNCLI10.1;".Length);
            RW = RW.Remove(RW.IndexOf("Application"),RW.Length - RW.IndexOf("Application"));



            MessageBox.Show(RW);

            //get the last insertion date from the SSASLoging table
            using (DataContext RWData = new DataContext(RW))
            {
                Table<SSASLogging> records = RWData.GetTable<SSASLogging>();
                var rs = (from r in records
                         select r.TimeStamp).Max();
                //result = rs.FirstOrDefault();
            }

        }

        catch (Exception e)
        {
            MessageBox.Show("Exception in Retrieving latesttime" + e.Message + "/n"
                            + e.StackTrace);
        }

        return result;
   }

}//end partial class


[Table]  
public class SSASLogging  
{
    [Column(Name = "CREATED_TIMESTAMP")] 
    private DateTime timeStamp;

    public DateTime TimeStamp 
    {
        get { return this.TimeStamp; }
    }
}//End SSASLogging

Answer 1

如果 Max 不工作，那么这个怎么办:

var maxDate =
    (from r in records
     orderby r.TimeStamp descending
     select r.TimeStamp)
    .FirstOrDefault();