紧急求助,C#自定义纸张问题.
IntPtr pi = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(StructDevMode)));
  if (pi == IntPtr.Zero)
  return;
  try
  {
  settings.CopyToHdevmode(pi);
  StructDevMode devmode = (StructDevMode)Marshal.PtrToStructure(pi, typeof(StructDevMode));
  devmode.dmSize = (short)Marshal.SizeOf(typeof(StructDevMode));
  devmode.dmPaperSize = 0x100;
  devmode.dmPaperWidth = (short)(size.Width * 10); // 以0.1mm为单位的宽度 
  devmode.dmPaperLength = (short)(size.Height * 10); // 以0.1mm为单位的高度 
  devmode.dmFields = 14; // DM_PAPERSIZE | DM_PAPERLENGTH | DM_PAPERWIDTH;
  Marshal.StructureToPtr(devmode, pi, false);
  settings.SetHdevmode(pi);
  }
  catch { }
  finally
  {
  Marshal.FreeHGlobal(pi);
  }

这段代码经常报表"内存无效的错误",导致程序自动退出.无法Catch,有哪位大侠能帮我.

  [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
  internal struct StructDevMode
  {
  [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
  public String dmDeviceName;
  [MarshalAs(UnmanagedType.U2)]
  public short dmSpecVersion;
  [MarshalAs(UnmanagedType.U2)]
  public short dmDriverVersion;
  [MarshalAs(UnmanagedType.U2)]
  public short dmSize;
  [MarshalAs(UnmanagedType.U2)]
  public short dmDriverExtra;
  [MarshalAs(UnmanagedType.U4)]
  public int dmFields;
  [MarshalAs(UnmanagedType.I2)]
  public short dmOrientation;
  [MarshalAs(UnmanagedType.I2)]
  public short dmPaperSize;
  [MarshalAs(UnmanagedType.I2)]
  public short dmPaperLength;
  [MarshalAs(UnmanagedType.I2)]
  public short dmPaperWidth;
  [MarshalAs(UnmanagedType.I2)]
  public short dmScale;
  [MarshalAs(UnmanagedType.I2)]
  public short dmCopies;
  [MarshalAs(UnmanagedType.I2)]
  public short dmDefaultSource;
  [MarshalAs(UnmanagedType.I2)]
  public short dmPrintQuality;
  [MarshalAs(UnmanagedType.I2)]
  public short dmColor;
  [MarshalAs(UnmanagedType.I2)]
  public short dmDuplex;
  [MarshalAs(UnmanagedType.I2)]
  public short dmYResolution;
  [MarshalAs(UnmanagedType.I2)]
  public short dmTTOption;
  [MarshalAs(UnmanagedType.I2)]
  public short dmCollate;
  [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
  public String dmFormName;
  [MarshalAs(UnmanagedType.U2)]
  public short dmLogPixels;
  [MarshalAs(UnmanagedType.U4)]
  public int dmBitsPerPel;
  [MarshalAs(UnmanagedType.U4)]
  public int dmPelsWidth;
  [MarshalAs(UnmanagedType.U4)]
  public int dmPelsHeight;
  [MarshalAs(UnmanagedTy