フォームなどの Rectangle が画面内に収まるようにサイズや表示位置を調整する（マルチモニタ対応）

gistfile1.cs

private Rectangle AdjustmentWindowBounds(Rectangle bounds)
{
	var workarea = Screen.FromRectangle(bounds).WorkingArea;

	if (workarea.Contains(bounds) == false)
	{
		if (bounds.Width > workarea.Width)
		{
			bounds.Width = workarea.Width;
		}
		
		if (bounds.Height > workarea.Height)
		{
			bounds.Height = workarea.Height;
		}
		
		if (bounds.Right > workarea.Right)
		{
			bounds.Offset(workarea.Right - bounds.Right, 0);
		}
		
		if (bounds.Bottom > workarea.Bottom)
		{
			bounds.Offset(0, workarea.Bottom - bounds.Bottom);
		}
		
		if (bounds.Left < workarea.Left)
		{
			bounds.Offset(workarea.Left - bounds.Left, 0);
		}
		
		if (bounds.Top < workarea.Top)
		{
			bounds.Offset(0, workarea.Top - bounds.Top);
		}
	}

	return bounds;
}