public partial class Form1 : Form
    {
        Bitmap memBitmap;
        float currRotation = 10;
        Rectangle rect = new Rectangle(100, 50, 150, 100);
        public Form1()
        {
            InitializeComponent();
            memBitmap = new Bitmap(this.Width, this.Height);
            using (Graphics g = Graphics.FromImage(memBitmap))
            {
                g.DrawRectangle(Pens.Blue, rect);
            }
        }
        protected override void OnMouseWheel(MouseEventArgs e)
        {
            currRotation -= 5.0f * e.Delta / SystemInformation.MouseWheelScrollDelta;     // 5 degree, you can make it 45
            
        }