Program rysujący figury nie działa :( C#

Witam. 

Zrobiłem coś co powinno rysować wybrana figurę niestety program nie działa.

W kodzie są takie obiekty jak:

textBox1 - wpisywanie dlugosci a lub r

textBox2 -wpisywanie dl b (tam gdzie potrzebne (kwadrat trojkat)

textBox3- wspolrzena x

textBox4- wsp y

ComboBox -> Selekcja figury - index 0 kwadrat, 1 prostokat,2 trojkat,3 koło

oto kod (program kompiluje sie poprawnie ale nic nie rysuje :(

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace WindowsFormsApplication3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }                    
        private void Form1_Load(object sender, EventArgs e)
        {
            Wyczysc_button.Visible = false;
        }
        private void formula_wyczysc()
        {
            Wyczysc_button.Visible = true;
            Rysuj_button.Visible = false;
            textBox1.Enabled = false;
            textBox2.Enabled = false;
            textBox3.Enabled = false;
            textBox4.Enabled = false;
            comboBox1.Enabled = false;
            comboBox2.Enabled = false;
       }
        //zdarzenie dla przycisku rysuj
        private void button1_Click(object sender, EventArgs e)
        {
            try
            {
                if (textBox1.Text != ""&& textBox3.Text != ""&& textBox4.Text != "")
                {
                    //kwadrat
                    if (comboBox1.SelectedIndex == 0)
                    {
                        int wsp_x, wsp_y, dl_a;
                        dl_a = int.Parse(textBox1.Text);
                        wsp_x = int.Parse(textBox3.Text);
                        wsp_y = int.Parse(textBox4.Text);
                        Kwadrat square = new Kwadrat(CreateGraphics());
                        square.create(wsp_x, wsp_y, dl_a);
                        formula_wyczysc();
                    }
                    //prostokat
                    else if (comboBox1.SelectedIndex == 1)
                    {
                        int wsp_x, wsp_y, dl_a, dl_b;
                        dl_a = int.Parse(textBox1.Text);
                        dl_b = int.Parse(textBox2.Text);
                        wsp_x = int.Parse(textBox3.Text);
                        wsp_y = int.Parse(textBox4.Text);
                        Prostokat rectangle = new Prostokat(CreateGraphics());
                        rectangle.create(wsp_x, wsp_y, dl_a, dl_b);
                        formula_wyczysc();
                    }
                    //trojkat
                    else if (comboBox1.SelectedIndex == 2)
                    {
                        int wsp_x, wsp_y, dl_a, dl_h;
                        dl_a = int.Parse(textBox1.Text);
                        dl_h = int.Parse(textBox2.Text);
                        wsp_x = int.Parse(textBox3.Text);
                        wsp_y = int.Parse(textBox4.Text);
                        Trojkat triangle = new Trojkat(CreateGraphics());
                        triangle.create(wsp_x,wsp_y,dl_a,dl_h);
                        formula_wyczysc();
                    }
                    //kolo
                    else if (comboBox1.SelectedIndex == 3)
                    {
                        int wsp_x, wsp_y, dl_r;
                        dl_r = int.Parse(textBox1.Text);
                        wsp_x = int.Parse(textBox3.Text);
                        wsp_y = int.Parse(textBox4.Text);
                        Kolo circle = new Kolo(CreateGraphics());
                        circle.create(wsp_x, wsp_y, dl_r);
                        formula_wyczysc();
                    }
                }
            }
            catch
            {
                MessageBox.Show("Złe dane! Spróbój ponownie:)","Error", MessageBoxButtons.OK);
            }
        }
 
        private void Wyczysc_button_Click(object sender, EventArgs e)
        {
             
        }
        //selekcja figur
        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            //kwadrat
         if(comboBox1.SelectedIndex==0)
            {
                textBox1.Visible = true;
                textBox1.Text = "bok a";
                textBox2.Visible = false;
                textBox3.Visible = true;
                textBox3.Text = "x";
                textBox4.Visible = true;
                textBox4.Text = "y";
            }
            //prostokat
            else if (comboBox1.SelectedIndex == 1)
            {
                textBox1.Visible = true;
                textBox1.Text = "bok a";
                textBox2.Visible = true;
                textBox2.Text = "bok b";
                textBox3.Visible = true;
                textBox3.Text = "x";
                textBox4.Visible = true;
                textBox4.Text = "y";
            }
            //trojkat
            else if (comboBox1.SelectedIndex == 2)
            {
                textBox1.Visible = true;
                textBox1.Text = "bok a";
                textBox2.Visible = true;
                textBox2.Text = "wysokosc h";
                textBox3.Visible = true;
                textBox3.Text = "x";
                textBox4.Visible = true;
                textBox4.Text = "y";
            }
            //kolo
            else if (comboBox1.SelectedIndex == 3)
            {
                textBox1.Visible = true;
                textBox1.Text = "promień r";
                textBox2.Visible = false;
                textBox3.Visible = true;
                textBox3.Text = "x";
                textBox4.Visible = true;
                textBox4.Text = "y";
            }
 
        }
    }
    class Kwadrat
    {
        public Kwadrat(Graphics graph)
        {
            g = graph;
        }
 
        Graphics g;
        Rectangle r;
        Pen p;
        public void create(int KW_wsp_x, int KW_wsp_y, int KW_dl_a)
        {
            p = new Pen(Brushes.DarkGreen);
            r = new Rectangle(KW_wsp_x, KW_wsp_y, KW_dl_a, KW_dl_a);
            g.DrawRectangle(p, r);
        }
    }
    class Trojkat
    {
        public Trojkat(Graphics graph)
        {
            g = graph;
        }
        Graphics g;
        public void create(int x, int y, int a, int h)
        {
            Pen blackPen = new Pen(Color.Black, 3);
 
            Point point1 = new Point(x, y);
            Point point2 = new Point(x, (y+h));
            Point point3 = new Point((x+h), y);
            Point[] curvePoints = { point1, point2, point3 };
                          
 
            // Draw polygon to screen.
            g.DrawPolygon(blackPen, curvePoints);
        }
    }
    class Prostokat
    {
        public Prostokat(Graphics graph)
        {
            g = graph;
        }
        Graphics g;
        Rectangle r;
        Pen p;
 
        public void create(int KW_wsp_x, int KW_wsp_y, int KW_dl_a, int KW_dl_b)
        {
            p = new Pen(Brushes.DarkGreen);
            r = new Rectangle(KW_wsp_x, KW_wsp_y, KW_dl_a, KW_dl_b);
            g.DrawRectangle(p, r);
        }
    }
    class Kolo
    {
        public Kolo(Graphics graph)
        {
            g = graph;
        }
        Graphics g;
        Pen p;
 
        public void create(int KW_wsp_x, int KW_wsp_y, int KW_dl_r)
        {
            p = new Pen(Brushes.Green);
            g.DrawEllipse(p, KW_dl_r, KW_dl_r,KW_wsp_x, KW_wsp_y);
        }
    }
}