我在实体框架中有一个名为雇佣的SQL Server表,其中有一个名为ID的键列。

如何使用实体框架从表中删除单个记录?


当前回答

你可以在网格的点击或celldoubleclick事件中这样做(如果你使用了一个)

if(dgEmp.CurrentRow.Index != -1)
 {
    employ.Id = (Int32)dgEmp.CurrentRow.Cells["Id"].Value;
    //Some other stuff here
 }

然后在删除按钮中执行如下操作:

using(Context context = new Context())
{
     var entry = context.Entry(employ);
     if(entry.State == EntityState.Detached)
     {
        //Attached it since the record is already being tracked
        context.Employee.Attach(employ);
     }                             
     //Use Remove method to remove it virtually from the memory               
     context.Employee.Remove(employ);
     //Finally, execute SaveChanges method to finalized the delete command 
     //to the actual table
     context.SaveChanges();

     //Some stuff here
}

或者,你可以使用LINQ查询,而不是使用LINQ到实体查询:

var query = (from emp in db.Employee
where emp.Id == employ.Id
select emp).Single();

雇佣。Id用作过滤参数,它已经从DataGridView的CellDoubleClick事件中传递。

其他回答

不需要先查询对象,可以通过它的id将它附加到上下文。 是这样的:

var employer = new Employ { Id = 1 };
ctx.Employ.Attach(employer);
ctx.Employ.Remove(employer);
ctx.SaveChanges();

或者,你可以将附加条目的状态设置为已删除:

var employer = new Employ { Id = 1 };
ctx.Entry(employer).State = EntityState.Deleted;
ctx.SaveChanges();

最好的办法是检查,然后删除

        if (ctx.Employ.Any(r=>r.Id == entity.Id))
        {
            Employ rec = new Employ() { Id = entity.Id };
            ctx.Entry(rec).State = EntityState.Deleted;
            ctx.SaveChanges();
        }

使用EntityFramework。Plus可以是一个选项:

dbContext.Employ.Where(e => e.Id == 1).Delete();

这里有更多的例子

更普通的approuch

public virtual void Delete<T>(int id) where T : BaseEntity, new()
{
    T instance = Activator.CreateInstance<T>();
    instance.Id = id;
    if (dbContext.Entry<T>(entity).State == EntityState.Detached)
    {
        dbContext.Set<T>().Attach(entity);
    }

    dbContext.Set<T>().Remove(entity);
}

你可以像这样简单地做

   public ActionResult Delete(int? id)
    {
        using (var db = new RegistrationEntities())
        {
            Models.RegisterTable Obj = new Models.RegisterTable();
            Registration.DAL.RegisterDbTable personalDetail = db.RegisterDbTable.Find(id);
            if (personalDetail == null)
            {
                return HttpNotFound();
            }
            else
            {
                Obj.UserID = personalDetail.UserID;
                Obj.FirstName = personalDetail.FName;
                Obj.LastName = personalDetail.LName;
                Obj.City = personalDetail.City;

            }
            return View(Obj);
        }
    }


    [HttpPost, ActionName("Delete")]

    public ActionResult DeleteConfirmed(int? id)
    {
        using (var db = new RegistrationEntities())
        {
            Registration.DAL.RegisterDbTable personalDetail = db.RegisterDbTable.Find(id);
            db.RegisterDbTable.Remove(personalDetail);
            db.SaveChanges();
            return RedirectToAction("where u want it to redirect");
        }
    }

模型

 public class RegisterTable
{

    public int UserID
    { get; set; }


    public string FirstName
    { get; set; }


    public string LastName
    { get; set; }


    public string Password
    { get; set; }


    public string City
    { get; set; }

} 

从视图中调用它

 <table class="table">
    <tr>
        <th>
            FirstName
        </th>
        <th>
            LastName
        </th>

        <th>
            City
        </th>
        <th></th>
    </tr>

    @foreach (var item in Model)
    {
        <tr>
            <td> @item.FirstName </td>
            <td> @item.LastName </td>
            <td> @item.City</td>
            <td>
                <a href="@Url.Action("Edit", "Registeration", new { id = item.UserID })">Edit</a> |
                <a href="@Url.Action("Details", "Registeration", new { id = item.UserID })">Details</a> |
                <a href="@Url.Action("Delete", "Registeration", new { id = item.UserID })">Delete</a>

            </td>
        </tr>

    }

</table>

我希望这对你来说很容易理解