private void button1_Click(object sender, System.EventArgs e)
{
   this.Close();
}

private Point mouse_offset;

private void Form1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
      mouse_offset = new Point(-e.X, -e.Y);
}

private void Form1_MouseMove(object sender, 
 System.Windows.Forms.MouseEventArgs e)
{
   if (e.Button == MouseButtons.Left) 
   {
      Point mousePos = Control.MousePosition;
      mousePos.Offset(mouse_offset.X, mouse_offset.Y);
      Location = mousePos;
   }
}

private void CustomButton_Paint(object sender, 
System.Windows.Forms.PaintEventArgs e)
{
   //初始化一个GraphicsPath类的对象
   System.Drawing.Drawing2D.GraphicsPath myGraphicsPath  = new 
System.Drawing.Drawing2D.GraphicsPath();
   //确定一个字符串，该字符串就是控件的形状
   string stringText = "Click Me!";
   //确定字符串的字体
   FontFamily family = new FontFamily("Arial");
   //确定字符串的风格
   int fontStyle = (int)FontStyle.Bold;
   //确定字符串的高度
   int emSize = 35;
   //确定字符串的起始位置，它是从控件开始计算而非窗体
   PointF origin = new PointF(0, 0);
   //一个StringFormat对象来确定字符串的字间距以及对齐方式
   StringFormat format = new StringFormat(StringFormat.GenericDefault);
   //用AddString方法创建字符串
   myGraphicsPath.AddString(stringText, family, fontStyle, emSize, origin, format);
   //将控件的Region属性设置为上面创建的GraphicsPath对象
   CustomButton.Region = new Region(myGraphicsPath);
}

private void CustomButton_Click(object sender, System.EventArgs e)
{
   CustomButton.BackColor = Color.BlanchedAlmond;
}

private void button1_Paint(object sender, 
System.Windows.Forms.PaintEventArgs e)
{
   System.Drawing.Drawing2D.GraphicsPath myGraphicsPath  = new
System.Drawing.Drawing2D.GraphicsPath();
   myGraphicsPath.AddEllipse(new Rectangle(0, 0, 125, 125));
   myGraphicsPath.AddEllipse(new Rectangle(75, 75, 20, 20));
   myGraphicsPath.AddEllipse(new Rectangle(120, 0, 125, 125));
   myGraphicsPath.AddEllipse(new Rectangle(145, 75, 20, 20));
   //改变按钮的背景颜色使之能被容易辨认
   button1.BackColor = Color.Chartreuse;
   button1.Size = new System.Drawing.Size(256, 256);
   button1.Region = new Region(myGraphicsPath);

}

protected override void  OnPaint(PaintEventArgs e)
或是this.Paint += new System.Windows.Form.PaintEventHandler(Form_Paint)。

private void Form_Paint(object sender, PaintEventArgs e)
	{
		Graphics g = e.Graphics;
			Rectangle mainRect = new Rectangle(0, 0, 695, 278);
			Region mainRegion = new Region(mainRect);
			e.Graphics.SetClip(mainRegion, CombineMode.Replace);
    			Point point1 = new Point(0, 32);
			Point point2 = new Point(9, 20);
			Point point3 = new Point(21, 13);
			Point point4 = new Point(34, 9);
    			// 创建一个以点为元素的数组
			Point[] curvePoints = { point1, point2, point3, point4 };
			// 创建一个GraphicsPath对象并添加一条曲线
			GraphicsPath myPath = new GraphicsPath();
			myPath.AddCurve(curvePoints, 0, 3, 0.8f);
			myPath.AddLine(36, 9, 378, 9);
			point1.X=378;point1.Y=9;
			point2.X=387;point2.Y=5;
			point3.X=394;point3.Y=0;
			Point[] curvePoints2 = { point1, point2, point3 };
			myPath.AddCurve(curvePoints2, 0, 2, 0.8f);
			myPath.AddLine(394, 0, 0, 0);
			Region ExcludeRegion3 = new Region(myPath);
			e.Graphics.ExcludeClip(ExcludeRegion3);

			GraphicsPath myPath3 = new GraphicsPath();
			point1.X=0;point1.Y=180;
			point2.X=19;point2.Y=198;
			point3.X=62;point3.Y=204;
			point4.X=83;point4.Y=221;
			Point point5 = new Point(93, 248);
			Point point6 = new Point(102, 267);
			Point point7 = new Point(125, 278);
			Point[] curvePoints3 = { point1, point2, point3, point4, 
point5, point6, point7 };
			myPath3.AddCurve(curvePoints3, 0, 6, 0.8f);
			myPath3.AddLine(125, 278, 90, 300);
			myPath3.AddLine(90, 300, 0, 300);
			Region ExcludeRegion2 = new Region(myPath3);
			e.Graphics.ExcludeClip(ExcludeRegion2);
			point1.X=454;point1.Y=0;
			point2.X=470;point2.Y=12;
			point3.X=481;point3.Y=34;
			Point[] curvePoints4 = { point1, point2, point3 };
			GraphicsPath myPath2 = new GraphicsPath();
			myPath2.AddCurve(curvePoints4, 0, 2, 0.8f);
			myPath2.AddLine(481, 30, 481, 76);
			myPath2.AddLine(481, 76, 495, 76);
			myPath2.AddLine(495, 76, 495, 0);
			Region ExcludeRegion4 = new Region(myPath2);
			e.Graphics.ExcludeClip(ExcludeRegion4);
			GraphicsPath myPath5 = new GraphicsPath();
			point1.X=481;point1.Y=76;
			point2.X=494;point2.Y=115;
			point3.X=481;point3.Y=158;
			Point[] curvePoints5 = { point1, point2, point3 };
			myPath5.AddCurve(curvePoints5, 0, 2, 0.8f);
			myPath5.AddLine(481, 158, 481, 279);
			myPath5.AddLine(481, 255, 495, 279);
			myPath5.AddLine(495, 279, 495, 0);
			Region ExcludeRegion6 = new Region(myPath5);
			e.Graphics.ExcludeClip(ExcludeRegion6);

			point1.X=480;point1.Y=250;
			point2.X=469;point2.Y=264;
			point3.X=446;point3.Y=278;
			Point[] curvePoints6 = { point1, point2, point3 };
			GraphicsPath myPath4 = new GraphicsPath();
			myPath4.AddCurve(curvePoints6, 0, 2, 0.8f);
			myPath4.AddLine(450, 277, 495, 279);
			Region ExcludeRegion5 = new Region(myPath4);
			e.Graphics.ExcludeClip(ExcludeRegion5);

			e.Graphics.DrawImage(img, 0, 0, 695,278);

			// 重设剪切好的区域
			e.Graphics.ResetClip();
	}