C#调用WIN32API系列二列举局网内共享打印机
 C#通过调用WIN32API可以实现非常强大的功能，本文将着重讲述如何通过调用WIN32API实现列举局域网络内所有共享的打印机。
 首先我们看看EnumPrinters函数的定义
BOOL EnumPrinters(
  DWORD Flags,         // printer object types
  LPTSTR Name,         // name of printer object
  DWORD Level,         // information level
  LPBYTE pPrinterEnum, // printer information buffer
  DWORD cbBuf,         // size of printer information buffer
  LPDWORD pcbNeeded,   // bytes received or required
  LPDWORD pcReturned   // number of printers enumerated
);
 这个api有几个返回参数, 其中最重要的是pPrinterEnum所指的缓冲区中，是一个
PRINTER_INFO_N的结构数组, 这里N根据Level参数而变化, 这里我们用的是1, 所以用到的结构是
typedef struct _PRINTER_INFO_1 {
  DWORD  Flags;
  LPTSTR pDescription;
  LPTSTR pName;
  LPTSTR pComment;
} PRINTER_INFO_1

C#要调用API首先要引入动态库，EnumPrinters在winspool.drv这个动态库中。引入语句如下
[DllImport("winspool.drv", CharSet=CharSet.Auto)]
然后是定义PRINTER_INFO_1结构
  [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
  struct PRINTER_INFO_1
 {
  int flags;
  [MarshalAs(UnmanagedType.LPTStr)]
  public string pDescription;
  [MarshalAs(UnmanagedType.LPTStr)]
  public string pName;
  [MarshalAs(UnmanagedType.LPTStr)]
  public string pComment;
 }
 好了，全部的源代码如下：
using System;
using System.Collections;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.Drawing.Printing;
public class QuickTest {
 [DllImport("winspool.drv", CharSet=CharSet.Auto)]
 static extern bool EnumPrinters(int flags, string name, int level, IntPtr pPrinterEnum,
  int cbBuf, out int pcbNeeded, out int pcReturned);
 
 private const int PRINTER_ENUM_NETWORK = 0x00000040;
 private const int PRINTER_ENUM_LOCAL = 0x00000002;
 private const int PRINTER_ENUM_REMOTE      = 0x00000010;
 [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
  struct PRINTER_INFO_1
 {
  int flags;
  [MarshalAs(UnmanagedType.LPTStr)]
  public string pDescription;
  [MarshalAs(UnmanagedType.LPTStr)]
  public string pName;
  [MarshalAs(UnmanagedType.LPTStr)]
  public string pComment;
 }
 
 public void EnumeratePrintersWin()
 {
  bool Success;
  int cbRequired;
  int nEntries;
  
  IntPtr outb = IntPtr.Zero;
    
  Success = EnumPrinters(PRINTER_ENUM_NETWORK | PRINTER_ENUM_LOCAL | PRINTER_ENUM_REMOTE, null , 1, outb, 0, out cbRequired, out nEntries);
  outb = Marshal.AllocHGlobal(cbRequired);
  Success = EnumPrinters(PRINTER_ENUM_NETWORK | PRINTER_ENUM_LOCAL | PRINTER_ENUM_REMOTE, null , 1, outb, cbRequired, out cbRequired, out nEntries);
  
  PRINTER_INFO_1[] portsArray = new PRINTER_INFO_1[cbRequired];
  

  IntPtr current = outb;
  try {
   for (int i=0; i<portsArray.Length; i++)
   {
    portsArray[i] = (PRINTER_INFO_1) Marshal.PtrToStructure(current,
     typeof(PRINTER_INFO_1));
    current=(IntPtr)((int)current+Marshal.SizeOf(typeof(PRINTER_INFO_1)));
    Console.WriteLine(i+": \n"+portsArray[i].pName+"\n"+portsArray[i].pDescription+"\n"+portsArray[i].pComment+"\n");
   }
  }
  catch (Exception) {
   //Console.WriteLine(exp.StackTrace);
  }
  Marshal.FreeHGlobal(outb);
 }
 public QuickTest () {

 }
 public static void Main() {
  QuickTest qt = new QuickTest();
  qt.EnumeratePrintersWin();
 }
}
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