C-Sharp App füllt bei Bilderwechsel den RAM

 private void timer1_Tick(object sender, EventArgs e)
        {
            cou = listBox1.SelectedIndex;
            
            //pictureBox1.Image = imageList1.Images[cou];
            
            
            cou++;
            if (cou > imageList1.Images.Count-1)
                cou = 0;

            listBox1.SelectedIndex = cou;
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            if (textBox1.Text != "" && Convert.ToInt32(textBox1.Text) > 0)  
                timer1.Interval = Convert.ToInt32(textBox1.Text) * 1000;
        }

        private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
             
            pictureBox1.Image = Image.FromFile(bildpfad[listBox1.SelectedIndex]);
            Properties.Settings.Default.Dia = listBox1.SelectedIndex;
        }
    }