semi-transparent form but opaque Controls in C#

Question

How to make semi transparent form in C# windows form application

I have tried the TransparentKey which makes it full-transparent. and tried Opacit

Answer 1

I found the Hatch Brush grotesque,

Instead of:

protected override void OnPaintBackground(PaintEventArgs e) {
  var hb = new HatchBrush(HatchStyle.Percent80, this.TransparencyKey);
  e.Graphics.FillRectangle(hb, this.DisplayRectangle);
}

I used:

protected override void OnPaintBackground(PaintEventArgs e) {
  var sb = new SolidBrush(Color.FromArgb(100, 100, 100, 100));
  e.Graphics.FillRectangle(sb, this.DisplayRectangle);
}