Assuming that saving an image of the entire
visual contents of the Panel is your goal:
using System.Drawing;
using System.Drawing.Imaging;
private void SavePanel1Contents_Click(object sender, EventArgs e)
{
int width = panel1.Width;
int height = panel1.Height;
Bitmap bitMap = new Bitmap(width, height);
panel1.DrawToBitmap(bitMap, new Rectangle(0, 0, width, height));
bitMap.Save(@"C:\Users\YourUserName\Desktop\TestSaveImageOfPanel1.png", ImageFormat.Png);
}