如何从表格中删除元素？

Question

Allow me to explain my situation.

I have a table in my database represented in my model by

   public Table<LinkDate> dates;

   [Table(Name = "dates")]
   public class LinkDate
   {
       public LinkDate()
       {

       }

       [Column(IsPrimaryKey = true)]
       public string linkguid { get; set; }
       [Column]
       public DateTime dtime { get; set; }

   }

which records the day/time that certain IDs were generated. These IDs are associated with one or more files in a table represented by

[Table( Name = "links")]
public class AssetLink
{
    public AssetLink()
    {

    }

    [Column(IsPrimaryKey = true, IsDbGenerated = true)]
    public int linkid { get; set; }
    [Column]
    public string linkguid { get; set; }
    [Column]
    public int fileid { get; set; }

}

I'm adding a functionality in my web application where a user can delete all links that are over a certain number of days old. Which means that if any such links exist, I will be deleting rows from both links and dates .

The action I've started to create is

    [HttpPost]
    public ActionResult FlushLinks (string numDaysOld)
    {
        // Deletes all database references to links were submitted over numDaysOld days ago

        DateTime currentDateTime = DateTime.Now;
        foreach (LinkDate thisLinkDate in PD.dates)
        {
            TimeSpan thisTimeSpan = new TimeSpan(Convert.ToInt16(numDaysOld), 0, 0, 0);
            if ((currentDateTime - thisLinkDate.dtime) > thisTimeSpan)
            {
                 // ...
            }

        }

        try 
        {
            PD.SubmitChanges();
        }
        catch (Exception ex)
        {
            return Content(ex.Message, "text/html");
        }

        // if here, everything went well
        return Content("Successfully removed all old links!", "text/html");
    }

and what I need help filling out is the // ... part because I don't know how to, and can't see any documentation about a way to , delete rows. What I'm trying to do is the equivalent of

 PD.links.Remove(x => x.linkguid == thisLinkDate.linkguid); // need something like this if possible
 thisLinkDate.Remove() // and need something like this if possible

What do I need to do?

Also, please let me know about any bugs you see in my procedure.

EDIT: I think I figured it out by myself:

foreach (AssetLink thislink in PD.links) if (thislink.linkguid == thisLinkDate.linkguid) PD.links.DeleteOnSubmit(thislink);
PD.dates.DeleteOnSubmit(thisLinkDate); 

If that's wrong, let me know

Answer 1

Try replacing your foreach loop with this.

DateTime currentDateTime = DateTime.Now;
TimeSpan thisTimeSpan = new TimeSpan(Convert.ToInt16(numDaysOld), 0, 0, 0);
var delete_list = PD.dates.Where(x => (currentDateTime - x.dtime) > thisTimeSpan)
PD.dates.RemoveRange(delete_list);

Answer 2

请注意，您只需要从日期表中删除，这将导致链接表中引用该日期的所有行的级联删除，前提是已为这些表正确配置了数据库的参照完整性检查。