DrawToBitmap doesn't work on panel

[Fr33dan]

So I've written a class that has a stores some test results info and then a control that displays that info to the user. I want to put a print function on this class to draw the control at a full page size and print it. However it always comes out blank. The code see the panel as a control because it could be some other type of value. I figure there must be something simple I'm missing.

void printDocument_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
        {
            System.Drawing.Size oldSize = printData.Size;

            printData.Size = new System.Drawing.Size(e.MarginBounds.Width, e.MarginBounds.Height);
            System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(printData.Size.Width, printData.Size.Height);

            InvertZOrderOfControls(printData.Controls);
            printData.DrawToBitmap(bitmap, new System.Drawing.Rectangle(0, 0, printData.Size.Width, printData.Size.Height));
            InvertZOrderOfControls(printData.Controls);
            
            e.Graphics.DrawImage(bitmap, e.MarginBounds.Location);
            bitmap.Save(@"C:\Users\jdudley\Documents\File.bmp");
            printData.Size = oldSize;
        }

The save call was added for debugging. It looks like it's actually rendering the background color of the panel without any of the controls.

[Plater]

Did you try taking out the zorder change and see if it helps?

[Fr33dan]

Sorry, I forgot about this post when no one responded and went to another forum.

It turns out a control can only be printed after it has been added window and drawn. In order to get this code to work as intended I had to show the item off screen before drawing to a bitmap. But in case the item was already being show on a dialog I had to include code to re-add it to it's original parent.

void printDocument_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
{
    System.Drawing.Size oldSize = printData.Size;
    System.Drawing.Color oldBackcolor = printData.BackColor;
    Control oldParent = printData.Parent;
    printData.Size = new System.Drawing.Size(e.MarginBounds.Width, e.MarginBounds.Height);
    printData.BackColor = Color.White;

    if (oldParent != null)
        oldParent.Controls.Remove(printData);

    handleForm = new Form();
    handleForm.Controls.Add(printData);
    handleForm.StartPosition = FormStartPosition.Manual;
    handleForm.Location = new Point(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height);

    handleForm.Show();

    Bitmap bitmap = new Bitmap(printData.Width, printData.Height);
    printData.DrawToBitmap(bitmap, new Rectangle(new Point(0, 0), printData.Size));
    
    e.Graphics.DrawImage(bitmap, e.MarginBounds.Location);

    handleForm.Controls.Remove(printData);
    if (oldParent != null)
        oldParent.Controls.Add(printData);
    handleForm.Close();

    printData.Size = oldSize;
    printData.BackColor = oldBackcolor;
}