枚举打印机（winapi）

using System;
using System.Runtime.InteropServices;
using System.Runtime.Serialization;

namespace Sample.GetPrinter
{
 class App
 {
  static void Main(string[] args)
  {
   Console.WriteLine("请输入你想搜索类型的序号:");
   Console.WriteLine("1. Default printer(only Win95,Win98,WinME)\n2. Enumerates the locally installed printers;\n3. Enumerates the list of printers to which the user has made previous connections;\n4. Enumerates the printer identified by Name.;\n5. Enumerates network printers and print servers in the computer's domain;\n6. Enumerates printers that have the shared attribute;\n7. Enumerates network printers in the computer's domain;\n======================================================================");
   
   int pt =0;
   try
   {
    pt=Int32.Parse(Console.ReadLine());
   }
   catch(Exception e)
   {
    Console.WriteLine("错误信息: {0}",e.Message);
    return;
   }

   PRINTER_ENUM printerKind = GetPrinterConType(pt);

   PrinterSearcher p = new PrinterSearcher();  

   PrinterSearcher.PrinterInfo[] printers = p.Search(printerKind);

   foreach(PrinterSearcher.PrinterInfo pi in printers)
   {
    Console.WriteLine("=====================================\n打印机名: {0}\n描叙:: {1}\n注释: {2}\n=====================================\n",
     pi.Name, pi.Description, pi.Comment);
   }
  }

  static PRINTER_ENUM GetPrinterConType(int ins)
  {
   switch(ins)
   {
    case 1:
     return PRINTER_ENUM.DEFAULT ;
    case 2:
     return PRINTER_ENUM.LOCAL;
    case 3:
     return PRINTER_ENUM.CONNECTIONS;
    case 4:
     return PRINTER_ENUM.NAME;
    case 5:
     return PRINTER_ENUM.REMOTE;
    case 6:
     return PRINTER_ENUM.SHARED;
    case 7:
     return PRINTER_ENUM.NETWORK;
    default:
     return PRINTER_ENUM.LOCAL ;
   }
  }
 }

 #region 打印机位置状态枚举 PRINTER_ENUM
 public enum PRINTER_ENUM
 {
  DEFAULT = 0x01,
  LOCAL = 0x02,
  CONNECTIONS = 0x04,
  NAME = 0x08,
  REMOTE = 0x10,
  SHARED = 0x20,
  NETWORK = 0x40
 }
 #endregion

 #region 异常派生 EnumPrinterException
 [Serializable]
 public class EnumPrinterException: ApplicationException
 {
  public EnumPrinterException() { }
  public EnumPrinterException (string message): base(message) { }
  public EnumPrinterException (string message, Exception inner):
   base(message, inner) {}
  protected EnumPrinterException (SerializationInfo info,
   StreamingContext context) : base(info, context)
  { }
 }
 #endregion

 //加上这个属性可以按导出到非托管对像的顺序排序
 [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
 public class PRINTER_INFO_1
 {
  public int flags;
  public IntPtr pDescription;
  public IntPtr pName;
  public IntPtr pComment;
 }

 public class PrinterSearcher
 {
  #region Search
  public PrinterInfo[] Search(PRINTER_ENUM printerKind)
  {
   PrinterInfo[] pInfo = new PrinterInfo[0];

   uint iNeeded = 0, iReturned = 0, iSize = 0;
   IntPtr printers = IntPtr.Zero;

     
   if (!EnumPrinters(printerKind, String.Empty,  1,  printers,  0, ref iNeeded, ref iReturned) )
   {
    //返回由上一个非托管函数返回的错误代码，该函数是使用设置了 -
    //DllImport属性中SetLastError=true 标志的平台调用来调用的

    int err = Marshal.GetLastWin32Error();
    if (err != Win32Error.ERROR_INSUFFICIENT_BUFFER)
     ThrowEnumPrinterException();
   }

   iSize = iNeeded;

   if (iNeeded != 0)
   {
    try
    {
     //使用AllocHGlobal分配非托管内块
     printers = Marshal.AllocHGlobal(new IntPtr(iSize));
     
     //如果调用不成功抛出异常
     if (!EnumPrinters(printerKind, String.Empty,1,printers, iSize, ref iNeeded, ref iReturned) )
     {
      ThrowEnumPrinterException();
     }
     else
     {
      pInfo = GetPrinterInfoFromMemory(printers, iReturned);
     }
    }
    finally
    {
     //释放分配的内存块
     if (printers != IntPtr.Zero)
      Marshal.FreeHGlobal(printers);
    }
   }
   return pInfo;
  }
  #endregion

  #region PrinterInfo
  public struct PrinterInfo
  {
   public string Name;
   public string Description;
   public string Comment;
  }

  
  public sealed class Win32Error
  {
   private Win32Error() {}
   public const int ERROR_INSUFFICIENT_BUFFER = 122;
  }
  #endregion

  #region EnumPrinters
  [DllImport("winspool.drv", SetLastError = true, CharSet = CharSet.Auto)]
  [return: MarshalAs(UnmanagedType.Bool)]
  private static extern bool EnumPrinters ([MarshalAs(UnmanagedType.U4)] PRINTER_ENUM flags,
   [MarshalAs(UnmanagedType.LPStr)] string sName,
   uint iLevel,
   IntPtr pPrinterDesc,
   uint iSize,
   [MarshalAs(UnmanagedType.U4)] ref uint iNeeded,
   [MarshalAs(UnmanagedType.U4)] ref uint iReturned
   );
  #endregion

  #region GetPrinterInfoFromMemory
  private PrinterInfo[] GetPrinterInfoFromMemory(IntPtr prInfo, uint numPrinters)
  {
   PRINTER_INFO_1 pi = new PRINTER_INFO_1();
         
   PrinterInfo[] pInfo = new PrinterInfo[numPrinters];

   for(int i = 0; i < numPrinters; i++)
   {
    //把数据从非托管内存传送到到托管内存
    Marshal.PtrToStructure(prInfo, pi);
         
    pInfo[i].Name = Marshal.PtrToStringAuto(pi.pName);
    pInfo[i].Description = Marshal.PtrToStringAuto(pi.pDescription);
    pInfo[i].Comment = Marshal.PtrToStringAuto(pi.pComment);

    prInfo =  new IntPtr(prInfo.ToInt32() + Marshal.SizeOf(typeof(PRINTER_INFO_1)));
   }
   return pInfo;
  }

  private void ThrowEnumPrinterException()
  {
   throw new EnumPrinterException(string.Format("LastErrorCode: {0}",
    Marshal.GetLastWin32Error()));
  }
  #endregion
 }
}

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