Need to create a textbox as curved shape inside the picturebox

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C#

I have a curved shaped textbox by using the class while I am dragging the curved shaped textbox in screen it shows correctly while I am fetching the same textbox inside picture box the shape doesn't shown....pls guide

What I have tried:

using System;
using System.Collections.Generic;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Drawing;

namespace RoundTextBox
{
   public class ceLearningTextbox : Control
    {
        private int radius = 15;
        public TextBox textBox = new TextBox();
        private GraphicsPath shape;
        private GraphicsPath innerRect;
        private Color br;

        public ceLearningTextbox()
        {
            base.SetStyle(ControlStyles.SupportsTransparentBackColor, true);
            base.SetStyle(ControlStyles.UserPaint, true);
            base.SetStyle(ControlStyles.ResizeRedraw, true);
            this.textBox.Parent = this;
            this.Controls.Add(this.textBox);
            this.textBox.BorderStyle = BorderStyle.None;
            textBox.Font = this.Font;
            this.BackColor = Color.Transparent;
            this.ForeColor = Color.Black;
            this.br = Color.White;
            textBox.BackColor = this.br;
            this.Text = null;
            this.Font = new Font("Century Gothic", 12f);
            base.Size = new Size(135, 33);
            this.DoubleBuffered = true;
            textBox.KeyDown += new KeyEventHandler(textbox_keydown);
            textBox.TextChanged += new EventHandler(textbox_TextChanged);
            textBox.MouseDoubleClick += new MouseEventHandler(textbox_MouseDoubleClick);

        }

        private void textbox_MouseDoubleClick(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                textBox.SelectAll();
            }
        }

        private void textbox_TextChanged(object sender, EventArgs e)
        {
            this.Text = textBox.Text;
        }

        private void textbox_keydown(object sender, KeyEventArgs e)
        {
            if(e.Control && (e.KeyCode == Keys.A))
            {
                textBox.SelectionStart = 0;
                textBox.SelectionLength = this.Text.Length;
            }
        }

        protected override void OnFontChanged(EventArgs e)
        {
            base.OnFontChanged(e);
            textBox.Font = this.Font;
            base.Invalidate();
        }

        protected override void OnForeColorChanged(EventArgs e)
        {
            base.OnForeColorChanged(e);
            textBox.ForeColor = this.ForeColor;
            base.Invalidate();
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            this.shape = new MyRectangle((float)base.Width, (float)base.Height, (float)this.radius, 0f, 0f).path;
            this.innerRect = new MyRectangle(base.Width - 0.5f, base.Height - 0.5f, (float)this.radius, 0.5f, 0.5f).path;
            if(textBox.Height >= (base.Height - 4))
            {
                base.Height = textBox.Height + 4;
            }
            textBox.Location = new Point(this.radius - 5, (base.Height / 2) - (textBox.Font.Height / 2));
            textBox.Width = base.Width - ((int)(this.radius * 1.5));
            e.Graphics.SmoothingMode = ((SmoothingMode)SmoothingMode.HighQuality);
            Bitmap bitmap = new Bitmap(base.Width, base.Height);
            Graphics graphics = Graphics.FromImage((Image)bitmap);
            e.Graphics.DrawPath(Pens.Black, this.shape);
            using(SolidBrush brush=new SolidBrush(this.br))
            {
                e.Graphics.FillPath((Brush)brush, this.innerRect);

            }
            Trans.Maketransparent(this, e.Graphics);
            base.OnPaint(e);
        }

        protected override void OnTextChanged(EventArgs e)
        {
            base.OnTextChanged(e);
            textBox.Text = this.Text;
        }
        public void selectAll()
        {
            textBox.SelectAll();
        }
        public Color Br
        {
            get =>
                this.br;
            set
            {
                this.br = value;
                if(this.br != Color.Transparent)
                {
                    textBox.BackColor = this.br;
                }
                base.Invalidate();
            }
        }

        public override Color BackColor 
        { 
            get => base.BackColor; 
            set => base.BackColor = Color.Transparent; 
        }
    }
}