C#呼叫WIN32API系列二列舉局網內共享印表機 (轉)

C#呼叫WIN32API系列二列舉局網內共享印表機 (轉)[@more@]

系列二列舉局網內共享印表機
 C#透過呼叫WIN32API可以實現非常強大的功能，本文將著重講述如何透過呼叫WIN32API實現列舉絡內所有共享的印表機。
 首先我們看看EnumPrinters的定義
BOOL EnumPrinters(
  D Flags,  // printer 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
);
 這個api有幾個返回引數, 其中最重要的是pPrinterEnum所指的緩衝區中，是一個
PRINTER_INFO_N的結構陣列, 這裡N根據Level引數而變化, 這裡我們用的是1, 所以用到的結構是
typedef struct _PRINTER_INFO_1 {
  DWORD  Flags;
  LPTSTR pDescription;
  LPTSTR pName;
  LPTSTR pComment;
} PRINTER_INFO_1

C#要呼叫API首先要引入動態庫，EnumPrinters在winspool.drv這個動態庫中。引入語句如下
[DllImport("winspool.drv", CharSet=CharSet.Auto)]
然後是定義PRINTER_INFO_1結構
 [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_ENUMWORK = 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[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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