protected void AddDeveloper_Click(object sender, EventArgs e)
        {
            List <int> categoryIds = new List <int>();

            foreach (ListItem item in LbCategories.Items)
            {
                if (item.Selected)
                {
                    categoryIds.Add(int.Parse(item.Value));
                }
            }
            var addedDeveloper = DbManager.AddDeveloper(TxtYazarAdi.Text, TxtYazarSoyadi.Text, TxtYazarUsername.Text, categoryIds);

            if (addedDeveloper.Success)
            {
                Application["Info"] = addedDeveloper.Message;
                Response.Redirect("Developers.aspx");
                Context.ApplicationInstance.CompleteRequest();
            }
            else
            {
                InfoLabel(addedDeveloper.Message);
            }
        }