最近做开发，要对POS打印机就进行编程，说白了，也就是一个端口读写，再根据打印机说明实现几个POS指令就OK了，但是遇到了一个困难的问题，因为是无人系统，一个打印机打印客户单据，一个打印历史单据，这个还不是最要命的，最要命的是一个是串口的，一个是并口的，对于串口还好办，因为.Net里有现成的SerialPort类，可是并口就难了。
搜了一下网上的资料，不外乎两种方法。
第一种是用win32 API来实现。见
http://support.microsoft.com/kb/823179/zh-cn
另一种方式是用第三方的动态连接库inpout32.dll
http://www.codeproject.com/KB/vb/Inpout32_read.aspx
两种方式，各有优劣。
如果用win32 API的话，操作固然方便，但是有一个死穴，就是无法读并口的数据。
如果用inpout32呢，到是能读能写，但是并口的地址（0x378,0x379,0x37a）并不是一个固定值。
参见文档
http://www.cnblogs.com/thunderdanky/articles/795010.html
但是客户要求能实时检测打印机状态 。。 这个问题可是难住了一天。
怎么办?让客户自己到设备管理器里去找并口基址？MS有点太土了。
后来看了一些资料，突然发现WQL好像可以实现查找串口基址的功能，实验了一下，还真实现了，嘿嘿
好了，现在就贴代码
Code
1using System;
2using System.Collections.Generic;
3using System.Text;
4using System.Runtime.InteropServices;
5using System.Management;
6
7namespace SFTech.POSPrint
8{
9 /**//// <summary>
10 /// 串口类，IPort是抽像的端口类
11 /// </summary>
12 public class ParallelPort : IPort ,IDisposable
13 {
14
15 inpout32相关#region inpout32相关
16 [DllImport("inpout32.dll", EntryPoint = "Out32")]
17 public static extern void Output(uint adress, int value);
18
19 [DllImport("inpout32.dll", EntryPoint = "Inp32")]
20 public static extern int Input(uint adress);
21 [StructLayout(LayoutKind.Sequential)]
22 private struct OVERLAPPED
23 {
24 int Internal;
25 int InternalHigh;
26 int Offset;
27 int OffSetHigh;
28 int hEvent;
29 }
30 #endregion
31
32 win32 API#region win32 API
33 [DllImport("kernel32.dll ")]
34 private static extern int CreateFile(
35 string lpFileName,
36 uint dwDesiredAccess,
37 int dwShareMode,
38 int lpSecurityAttributes,
39 int dwCreationDisposition,
40 int dwFlagsAndAttributes,
41 int hTemplateFile
42 );
43 [DllImport("kernel32.dll ")]
44 private static extern bool WriteFile(
45 int hFile,
46 byte[] lpBuffer,
47 int nNumberOfBytesToWrite,
48 ref int lpNumberOfBytesWritten,
49 ref OVERLAPPED lpOverlapped
50 );
51 [DllImport("kernel32.dll ")]
52 private static extern bool CloseHandle(
53 int hObject
54 );
55 [DllImport("kernel32.dll ")]
56 private static extern bool ReadFile(
57 int hFile,
58 out byte[] lpBuffer,
59 int nNumberOfBytesToRead,
60 ref int lpNumberOfBytesRead,
61 ref OVERLAPPED lpOverlapped
62 );
63
64 private int iHandle;
65
66 private bool _isWork;
67
68 private const uint GENERIC_READ = 0x80000000;
69 private const uint GENERIC_WRITE = 0x40000000;
70 #endregion
71 IPort 成员#region IPort 成员
72
73
74 private bool _IsOpen;
75 public bool IsOpen
76 {
77 get
78 {
79 return _IsOpen;
80 }
81 private set
82 {
83 _IsOpen = value;
84 }
85 }
86
87 private string _Name;
88 public string Name
89 {
90 get
91 {
92 return _Name;
93 }
94 set
95 {
96 _Name = value;
97 }
98 }
99
100 public bool WriteData(byte[] Data)
101 {
102 //for (int i = 0; i < Data.Length; i++)
103 // Output(BasePort, Data[i]); 这里原来也想用inpout32实现，但是从字节到int转换比较麻烦，试了几次没达到效果
104 //return true;
105
106 if (iHandle != -1)
107 {
108 OVERLAPPED x = new OVERLAPPED();
109 int i = 0;
110 WriteFile(iHandle, Data, Data.Length,
111 ref i, ref x);
112 return true;
113 }
114 else
115 {
116 //throw new Exception("不能连接到打印机! ");
117 return false;
118 }
119 }
120
121
122 /**//// <summary>
123 /// 读状态
124 /// 用inpout32
125 /// </summary>
126 /// <param name="Len"></param>
127 /// <returns></returns>
128 public byte[] ReadData(int Len)
129 {
130 byte[] result ;//= new byte[Len];
131 result = new byte[Len];
132 for (int i = 0; i < result.Length; i++)
133 result[i] = (byte)Input(BasePort + 1);
134 return result;
135 }
136
137
138 /**//// <summary>
139 /// 打开端口
140 /// </summary>
141 public void Open()
142 {
143 iHandle = CreateFile(Name, 0x40000000, 0, 0, 3, 0, 0);
144 if (iHandle != -1)
145 {
146 this.IsOpen = true;
147 }
148 else
149 {
150 this.IsOpen = false;
151 }
152
153 this.IsOpen = true;
154 _isWork = true;
155 //开一个线程检测状态口状态
156 new System.Threading.Thread(new System.Threading.ThreadStart(ReadState)).Start();
157 }
158
159
160 /**//// <summary>
161 /// 关闭端口
162 /// </summary>
163 public void Close()
164 {
165 this.IsOpen = !CloseHandle(iHandle);
166 _isWork = false;
167 }
168
169 /**//// <summary>
170 /// 端口基址
171 /// </summary>
172 private uint BasePort { get; set; }
173 internal ParallelPort(String portName)
174 {
175 this.Name = portName;
176 iHandle = -1;
177
178 /**////用wql查询串口基址
179 ManagementObjectSearcher search2 =
180 new ManagementObjectSearcher(
181 "ASSOCIATORS OF {Win32_ParallelPort.DeviceID='" + this.Name + "'}");
182 //本来最佳的wql是ASSOCIATORS OF {Win32_ParallelPort.DeviceID='" + this.Name + "'} WHERE ASSCICLASS = Win32_PortResource
183 //但是不知道为什么不返回结果，所以就做一个简单的遍历吧
184 foreach (var i in search2.Get())
185 {
186
187 if (i.ClassPath.ClassName == "Win32_PortResource")
188 {
189 //得到串口基址 大多数是0x378H
190 this.BasePort = System.Convert.ToUInt32( i.Properties["StartingAddress"].Value.ToString());
191
192 break;
193 }
194
195
196 }
197 if (BasePort == 0)
198 throw new Exception("不是有效端口");
199 IsOpen = false;
200 }
201
202 #endregion
203
204 IPort Members#region IPort Members
205
206 public event PortStateChanged StateChanged;
207
208 public event PortDataReceived DataReceive;
209
210 public System.Windows.Forms.Form Parent
211 {
212 get
213 {
214 throw new NotImplementedException();
215 }
216 set
217 {
218 throw new NotImplementedException();
219 }
220 }
221
222 private int a { get; set; }
223
224 /**//// <summary>
225 /// 检测线程，当状态改变时，引发事件
226 /// </summary>
227 private void ReadState()
228 {
229
230 a = 0;
231 int lastRead =a;
232 while (_isWork)
233 {
234 lastRead = a;
235 a = Input(BasePort + 1);
236 if (a != lastRead)
237 {
238 if (this.StateChanged != null)
239 {
240 PortChangedEvntAvrgs e = new PortChangedEvntAvrgs();
241 e.PortStatusByte = a;
242 this.StateChanged(this, e);
243 }
244
245 }
246 System.Threading.Thread.Sleep(500);
247
248 }
249 }
250 #endregion
251
252 IDisposable Members#region IDisposable Members
253
254 public void Dispose()
255 {
256 this.Close();
257 }
258
259 #endregion
260
261 IPort Members#region IPort Members
262
263
264 public void Update()
265 {
266 a = 0;
267 }
268
269 #endregion
270 }
271}
272