How to print all the Images of PictureBoxes in a FlowLayoutPanel

Question

I'm struggling to print all the images of PictureBox-es which are hosted by a FlowLayoutPanel container.

I've have tried this code but I'm getting an exception:

private void PrintAllImages()
{
    imagesToPrintCount = flowLayoutPanel1.Controls.Count;
    PrintDocument doc = new PrintDocument();
    doc.PrintPage += Document_PrintPage;
    PrintDialog dialog = new PrintDialog();
    dialog.Document = doc;

    if (dialog.ShowDialog() == DialogResult.OK)
        doc.Print();
}

private void Document_PrintPage(object sender, PrintPageEventArgs e)
{
    e.Graphics.DrawImage(GetNextImage(), e.MarginBounds);
    e.HasMorePages = imagesToPrintCount > 0;
}

private Image GetNextImage()
{
    //this line I get the error
    PictureBox pictureBox = (PictureBox)flowLayoutPanel2.Controls[flowLayoutPanel2.Controls.Count - imagesToPrintCount];

    imagesToPrintCount--;
    return pictureBox.Image;

}

The Exception:

System.ArgumentOutOfRangeException: 'Index -2 is out of range. Parameter name: index'

Answer 1

You can simplify the task by using the Queue class.

• Create a new Queue<Image>.
• Get the PictureBox-es from the FlowLayoutPanel and Enqueue their images.
• In the PrintPage event, Dequeue the next image and draw it until the queue is empty.

I'll shrink your code to the PrintAllImages() method as follows:

using System.Collections.Generic;
using System.Drawing.Printing;
//...

private void PrintAllImages()
{
    var queue = new Queue<Image>();

    flowLayoutPanel2.Controls.OfType<PictureBox>().Where(p => p.Image != null)
        .ToList().ForEach(p => queue.Enqueue(p.Image));

    if (queue.Count == 0) return;

    using (var doc = new PrintDocument())
    using (var pd = new PrintDialog())
    {
        pd.Document = doc;
        if(pd.ShowDialog() == DialogResult.OK)
        {
            doc.PrintPage += (s, e) =>
                {
                    e.Graphics.DrawImage(queue.Dequeue(), e.MarginBounds);
                    e.HasMorePages = queue.Count > 0;
                };
            pd.Document.Print();
        }
    }
}
//...