void UpdateTable()
        {
            comboBox1.Items.Clear();

            foreach (var item in db.Tables.OrderBy(c => c.Table_Number).ToList())
            {
                CategoryCombo com = new CategoryCombo
                {
                    Text  = item.Table_Number.ToString(),
                    Value = item.ID
                };
                comboBox1.Items.Add(com);
            }
        }
        void UpdateCategory()
        {
            cmbCategorySelect.Items.Clear();

            foreach (var item in db.Categories.OrderBy(c => c.Name).ToList())
            {
                CategoryCombo com = new CategoryCombo
                {
                    Text  = item.Name,
                    Value = item.ID
                };
                cmbCategorySelect.Items.Add(com);
            }
        }