Combobox Filter

 #region class List Combo test
        void fillTestGrid()//Fills grid with all categories
        {
            List<Screwfix> scr = sc.GetAllScrewfixResults();
            dgvTest.DataSource = scr;
        }

        void cbx1Test()//Fills combo1 with CategoryA
        {
            List<Screwfix> scr = sc.GetAllScrewfixResults();
            this.comboBox1.DataSource = scr.Select(s => s.CategoryA).Distinct().ToList();
            comboBox1.Text = "-Select-";
        }
        void cbx2Test()//Fills combo2 with CategoryB...not used in this example
        {
            List<Screwfix> scr = sc.GetAllScrewfixResults();
            this.comboBox2.DataSource = scr.Select(s => s.CategoryB).Distinct().ToList();
            comboBox2.Text = "-Select-";
        }

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            List<Screwfix> scr = sc.GetAllScrewfixResults();
            dgvTest.DataSource = scr.Where(x => x.CategoryA.Contains(comboBox1.Text)).ToList();

            if (comboBox1.Text == "Brackets")//CategoryA
            {
                comboBox2.Items.Clear();
                comboBox2.Text = "-Select-";
                comboBox2.Items.Add("Plates");//CatB
                comboBox2.Items.Add("Angled brackets");//CatB
                return;
            }
            else
            if (comboBox1.Text == "Plumbing")//CatA
            {
                comboBox2.Items.Clear();
                comboBox2.Text = "-Select-";
                comboBox2.Items.Add("Copper fittings");//CatB
                comboBox2.Items.Add("Fittings");
                comboBox2.Items.Add("Hoses and fittings");
                comboBox2.Items.Add("Soldering");
                comboBox2.Items.Add("Waste accessories");
                comboBox2.Items.Add("Waste pipe and fittings");
                comboBox2.Items.Add("Water pipe");
                return;
            }
            //comboBox2.Enabled = true;
        }
        private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
        {
            List<Screwfix> scr = sc.GetAllScrewfixResults();
            dgvTest.DataSource = scr.Where(x => x.CategoryB.Contains(comboBox2.Text)).ToList();
        }

        private void txtTest_TextChanged(object sender, EventArgs e)//Works as expected
        {
            List<Screwfix> scr = sc.GetAllScrewfixResults();
            dgvTest.DataSource = scr.Where(s => s.Description.ToLower().Contains(txtTest.Text.ToLower())).ToList();
        }
        #endregion