EntityFramework 如何按日期时间删除行

Question

I use layered architecture. I just started the Entity Framework. How can I delete lines by DateTime? I share the entities layer and dataAccess layer.

namespace Entities
{
    [Table("studentdetails")]
    public class GemkayDB : IEntity
    {
        [Key]
        public int ID { get; set; }
        public DateTime Time { get; set; }
        public string Type { get; set; }
        public string Name { get; set; }
        public string Explanation { get; set; }
    }
}

I want to delete according to DateTime.

public void Sil(GemkayDB gemkayDB)
{
    using (var baglanti = new GemkayDBContext())
    {
        var eklenenEntity = baglanti.Entry(gemkayDB);
        eklenenEntity.State = EntityState.Deleted;
        baglanti.SaveChanges();
    }
}        

For example Time <= Now.Months('-2') .

How can I do that?

Answer 1

The code you have written deleted items by primary key - you create some local entity that matches a DB entity and attach it to the local tracker, so effectively EF thinks it has downloaded it, then you set its state to deleted so that EF will think it has to issue a DELETE command to bring the entity in the db in sync with the local. This avoids downlaoding data from the DB, and just straight issues a delete for that entity with that primary key

If you want to delete entities in the same way based on some other field then you 'll have to create all the entities that would be affected, so they too can be deleted by their PK. If you don't know which entities you want to delete, you'll either have to query them from the DB (ie download the entities with the relevant datetimes, so that EF knows which to delete; yourContext.SomeEntities.RemoveRange(yourContext.SomeEntities.Where(x => x.Time < DateTime.Now.AddMonths(-2)) ), or you'll have to issue a raw sql that perfroms the delete server side, based on the time as a WHERE predicate (eg dbContext.Database.ExecuteSqlCommand("DELETE FROM studentdetails WHERE Time < DATE_ADD(month, -2, GetUtcDate())") )