How to delete in linq to sql?

Inserted_LINQDataContext db = new Inserted_LINQDataContext();
                Item itm = new Item();
                int ID = Convert.ToInt32(TextBox1.Text);
                var DeleteID = from d in db.Items
                               where d.id == ID
                               select d;
                db.Items.DeleteAllOnSubmit(DeleteID);
                db.SubmitChanges();
                Label2.Text = "Record deleted Successfully.";
                TextBox1.Text = "";

where Item is Table name, Linserted_LINQDataContext is your Linq DB name, id is the Column name in Item table. Items is the alias name of Item table in linq.

this is a simple way to delete row from table by linq query.may be it helps .

        var summary_delete = database.summeries.Find(id);

        var delete = database.summeries.Remove(summary_delete);

        database.SaveChanges();

reference : http://mvc4asp.blogspot.in/2013/09/how-to-delete-table-row-in-sql-database.html

        SupportDataDataContext Retrive = new SupportDataDataContext();
        //  SupportDataDataContext delete = new SupportDataDataContext();

        Topic res = Retrive.GetTable<Topic>().Single(t => t.ID == topicID);


        if (res != null)
        {
            Retrive.Topics.DeleteOnSubmit(res);
            Retrive.SubmitChanges(ConflictMode.ContinueOnConflict);
        }

You have several questions in your one question, but I will start with the simplest, about attaching, if you already have the primary key. If you don't have the primary key then I have always just done a fetch then a delete, but, whenever I do a fetch I tend to store the primary key for updates and deletes.

It will delete off of the primary key, but if you have that then just attach as I do below and call delete. I don't pass around the object needed by DLINQ as I want to be able to change it if I want, so I pass in a different User object and just pull the PK from the business class and put it into the DAO class.

var db = new MeatRequestDataContext();            
if (input.UserID > 0)
{
     entity = new User()
     {
         UserID = input.UserID
     };
     db.Users.Attach(entity);
     db.Users.DeleteOnSubmit(entity);
 }