CustomButton.cs

using System;
using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Drawing2D;

namespace HiraKata_Kaizen {
    public class CustomButton : Button {
        //Fields
        int borderSize = 0;
        int borderRadius = 10;
        Color borderColor = Color.Transparent;

        //Properties
        public int BorderSize {
            get { return borderSize; }
            set {
                borderSize = value;
                this.Invalidate();
            }
        }

        public int BorderRadius {
            get { return borderRadius; }
            set {
                borderRadius = value;
                this.Invalidate();
            }
        }

        public Color BorderColor {
            get { return borderColor; }
            set {
                borderColor = value;
                this.Invalidate();
            }
        }
        public Color BackgroundColor {
            get { return this.BackColor; }
            set { this.BackColor = value; }
        }

        public Color TextColor {
            get { return this.ForeColor; }
            set { this.ForeColor = value; }
        }

        //Constructor
        public CustomButton() {
            this.FlatStyle = FlatStyle.Flat;
            this.FlatAppearance.BorderSize = 0;
            this.Size = new Size(150, 40);
            this.BackColor = Color.FromArgb(30, 30, 34);
            this.ForeColor = Color.White;
            this.Resize += new EventHandler(Button_Resize);
        }

        void Button_Resize(object sender, EventArgs e) {
            if (borderRadius > this.Height)
                borderRadius = this.Height;
        }

        //Methods
        GraphicsPath GetFigurePath(Rectangle rect, float radius) {
            GraphicsPath path = new GraphicsPath();
            float curveSize = radius * 2F;
            path.StartFigure();
            path.AddArc(rect.X, rect.Y, curveSize, curveSize, 180, 90);
            path.AddArc(rect.Right - curveSize, rect.Y, curveSize, curveSize, 270, 90);
            path.AddArc(rect.Right - curveSize, rect.Bottom - curveSize, curveSize, curveSize, 0, 90);
            path.AddArc(rect.X, rect.Bottom - curveSize, curveSize, curveSize, 90, 90);
            path.CloseFigure();
            return path;
        }

        protected override void OnPaint(PaintEventArgs pevent) {
            base.OnPaint(pevent);

            Rectangle rectSurface = this.ClientRectangle;
            Rectangle rectBorder = Rectangle.Inflate(rectSurface, -borderSize, -borderSize);
            int smoothSize = 2;
            if (borderSize > 0)
                smoothSize = borderSize;

            if (borderRadius > 2) //Rounded button
            {
                using (GraphicsPath pathSurface = GetFigurePath(rectSurface, borderRadius))
                using (GraphicsPath pathBorder = GetFigurePath(rectBorder, borderRadius - borderSize))
                using (Pen penSurface = new Pen(this.Parent.BackColor, smoothSize))
                using (Pen penBorder = new Pen(borderColor, borderSize)) {
                    pevent.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
                    //Button surface
                    this.Region = new Region(pathSurface);
                    //Draw surface border for HD result
                    pevent.Graphics.DrawPath(penSurface, pathSurface);

                    //Button border                    
                    if (borderSize >= 1)
                        //Draw control border
                        pevent.Graphics.DrawPath(penBorder, pathBorder);
                }
            }
            else //Normal button
            {
                pevent.Graphics.SmoothingMode = SmoothingMode.None;
                //Button surface
                this.Region = new Region(rectSurface);
                //Button border
                if (borderSize >= 1) {
                    using (Pen penBorder = new Pen(borderColor, borderSize)) {
                        penBorder.Alignment = PenAlignment.Inset;
                        pevent.Graphics.DrawRectangle(penBorder, 0, 0, this.Width - 1, this.Height - 1);
                    }
                }
            }
        }

        protected override void OnHandleCreated(EventArgs e) {
            base.OnHandleCreated(e);
            this.Parent.BackColorChanged += new EventHandler(Container_BackColorChanged);
        }

        void Container_BackColorChanged(object sender, EventArgs e) {
            this.Invalidate();
        }

    }
}