How to make the background of a label transparent in c#

Question

I have form as in the image below.

I want to see label1 and label3 through label2. (I just want to see only the border of the label2). I have changed the BackColor in label2 to Transparent. But the result is same like the above picture.

Solution

In Windows Forms you can't do this directly. You can work with BackgroundImage.

Try this:

void TransparetBackground(Control C)
{
    C.Visible = false;

    C.Refresh();
    Application.DoEvents();

    Rectangle screenRectangle = RectangleToScreen(this.ClientRectangle);
    int titleHeight = screenRectangle.Top - this.Top;
    int Right = screenRectangle.Left - this.Left;

    Bitmap bmp = new Bitmap(this.Width, this.Height);
    this.DrawToBitmap(bmp, new Rectangle(0, 0, this.Width, this.Height));
    Bitmap bmpImage = new Bitmap(bmp);
    bmp = bmpImage.Clone(new Rectangle(C.Location.X+Right, C.Location.Y + titleHeight, C.Width, C.Height), bmpImage.PixelFormat);
    C.BackgroundImage = bmp;

    C.Visible = true;
}

and in Form_Load:

private void Form1_Load(object sender, EventArgs e)
{
    TransparetBackground(label2);
}

and you can see this result:

Comments

[A. Niese]

I realize this is for .NET Framework, but in .NET Core 3.1 Winforms, this generates an out of memory exception on the .Clone line.