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实现列举络内所有共享的打印机。
首先我们看看EnumPrinters的定义
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
);
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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