C#

[Designer(typeof(BaseControlDesigner))]
public abstract class BaseControl:Control
{
        public BaseControl()
        {                     
            this.DoubleBuffered = false;
            SetStyle(ControlStyles.SupportsTransparentBackColor, true);
            SetStyle(ControlStyles.Opaque, true);
            this.BackColor = Color.Transparent;                            
        }}

        protected override CreateParams CreateParams
        {
            get
            {
                CreateParams cp = base.CreateParams;
                cp.ExStyle |= 0x20; //WS_EX_TRANSPARENT 
                return cp;
            }
        }
        protected override void OnPaint(PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            Rectangle bounds = new Rectangle(0, 0, this.Width - 1, this.Height - 1);

            Color frmColor = this.Parent.BackColor;
            Brush bckColor;
            int alpha = 255;

            alpha = (this.Opacity * 255) / 100;
            

            if (this.drag)
            {
                Color dragBckColor;

                if (BackColor != Color.Transparent)
                {
                    int Rb = BackColor.R * alpha / 255 + frmColor.R * (255 - alpha) / 255;
                    int Gb = BackColor.G * alpha / 255 + frmColor.G * (255 - alpha) / 255;
                    int Bb = BackColor.B * alpha / 255 + frmColor.B * (255 - alpha) / 255;
                    dragBckColor = Color.FromArgb(Rb, Gb, Bb);
                }
                else dragBckColor = frmColor;

                alpha = 255;
                bckColor = new SolidBrush(Color.FromArgb(alpha, dragBckColor));
            }
            else
            {
                bckColor = new SolidBrush(Color.FromArgb(alpha, this.BackColor));
            }

            if (this.BackColor != Color.Transparent | drag)
            {
                g.FillRectangle(bckColor, bounds);
            }
            bckColor.Dispose();
            //base.OnPaint(e);
        }        
    }
}
    internal class BaseControlDesigner : ControlDesigner
    {
        private BaseControl myControl;

        protected override void OnMouseDragMove(int x, int y)
        {
            myControl = (BaseControl)(this.Control);
            myControl.drag = true;
            base.OnMouseDragMove(x, y);
        }

        protected override void OnMouseLeave()
        {
            myControl = (BaseControl)(this.Control);
            myControl.drag = false;
            base.OnMouseLeave();
        }
    }