protected void tree_CustomCallback(object sender, DevExpress.Web.ASPxTreeList.TreeListCustomCallbackEventArgs e)
    {
        if (String.IsNullOrWhiteSpace(e.Argument))
        {
            return;
        }
        var param = e.Argument.Split(';');

        if (param.Length < 2)
        {
            return;
        }
        var context     = new NorthwindDataClassesDataContext();
        var currentNode = context.Employees.Where(empl => empl.EmployeeID == Convert.ToInt32(param[0])).FirstOrDefault();
        var copyNode    = context.Employees.Where(empl => empl.EmployeeID == Convert.ToInt32(param[1])).FirstOrDefault();

        if (ProcessNodes(tree.FindNodeByKeyValue(copyNode.EmployeeID.ToString()), currentNode.EmployeeID.ToString()))
        {
            copyNode.ReportsTo = currentNode.EmployeeID;
            //coment the below line to enable updates
            throw new CallbackException("Updates aren't allowed in online demo");
            context.SubmitChanges();
            tree.DataBind();
        }
        else
        {
            throw new CallbackException("You're trying to move a parent node to its child");
        }
    }
        protected void Page_Load(object sender, EventArgs e)
        {
            using (var data =
                new NorthwindDataClassesDataContext())
            {
                var liste =
                    from a in data.Order_Details
                    group a by a.ProductID into g
                    select new
                    {
                        ProductID = g.Key,
                        TotalPrice = g.Sum(x => x.UnitPrice * x.Quantity)
                    };

                gv.DataSource = liste;
                gv.DataBind();
            }
        }
        protected void Page_Load(object sender, EventArgs e)
        {
            using (var data =
                new NorthwindDataClassesDataContext())
            {
                var liste = (
                    from a in data.Products
                    orderby a.UnitPrice descending
                    select new {
                        a.CategoryID, a.Category.CategoryName,
                        a.ProductID, a.ProductName,
                        a.UnitPrice
                    }).Take(10);

                gv.DataSource = liste;
                gv.DataBind();
            }
        }
        protected void Page_Load(object sender, EventArgs e)
        {
            using (var data =
                new NorthwindDataClassesDataContext())
            {
                var liste = (
                    from a in data.Products
                    orderby a.UnitPrice descending
                    select a).Take(20).ToList();

                gv.DataSource = liste;
                gv.DataBind();

                // var kullanımı
                var i = 0;
                //List<KeyValuePair<int, string>>

                // anonim tipler
                var tip = new { Ad = "Alper", Soyad = "Konuralp", No = 5 };
                string s = tip.Ad + " " + tip.Soyad;
            }
        }