How to make a UserControls BackColor transparent in C#?

Question

I created a simple stick man in a Windows Form User-Control (consisting of a radio button and three labels and one progress bar).

I set the back-color of the new use

Answer 1

Why all those things? UserControl class has property Region. Set this to what ever shape you like and no other adjustments are needed.

public partial class TranspBackground : UserControl
{
    public TranspBackground()
    {
        InitializeComponent();
    }

    GraphicsPath GrPath
    {
        get
        {
            GraphicsPath grPath = new GraphicsPath();
            grPath.AddEllipse(this.ClientRectangle);
            return grPath;
        }
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        // set the region property to the desired path like this
        this.Region = new System.Drawing.Region(GrPath);

        // other drawing goes here
        e.Graphics.FillEllipse(new SolidBrush(ForeColor), ClientRectangle);
    }

}

The result is as in the image below:

No low level code, no tweaking, simple and clean. There is however one issue but in most cases it can go undetected, the edges are not smooth and anti-aliasing will not help either. But the workaround is fairly easy. In fact much easier than all those complex background handling..