protected void Page_Load(object sender, EventArgs e)
        {
            GUIHandler = new GUIHandler();

            // Maak #select_skills leeg
            select_skills.Items.Clear();

            // Zet alle mogelijke skills in #select_skills
            List<Skilldetails> skills = GUIHandler.GetAllSkills();
            foreach (Skilldetails skill in skills)
            {
                select_skills.Items.Add(skill.Name);
            }
        }
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                // Check if GUIHandler exists
                if (Session["GUIHandler_obj"] == null)
                {
                    // Go back if no GUIhandler can be found
                    Response.Redirect("inloggen.aspx", false);
                    return;
                }

                // Retrieve GUIHandler object from session
                GUIHandler = (GUIHandler)Session["GUIHandler_obj"];

                // Empty select_skills
                select_skills.Items.Clear();

                // Add all skills in select_skills
                List<Skilldetails> skills = GUIHandler.GetAllSkills();
                foreach (Skilldetails skill in skills)
                {
                    select_skills.Items.Add(skill.Name);
                }

                selected_skills = new List<Skilldetails>();
            }
        }