从打印机打印时出现问题

Question

我正在创建一个桌面应用程序来从 Cognitive Advantage DLX 打印机打印标签。我正在尝试在 Visual C#.Net 中逐行打印。我的程序和打印机工作正常。我曾尝试从打印机中进行“测试打印”，它成功地进行了我的打印测试。但是当我尝试从打印机打印时，它不起作用。另外，我没有收到任何错误。

这是我在打印课上的代码，

 class LPrinter 
 32     {
 33        // Structure and API declarions:
 34        [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Ansi)]
 35        public class DOCINFOA
 36        {
 37           [MarshalAs(UnmanagedType.LPStr)] public string pDocName;
 38           [MarshalAs(UnmanagedType.LPStr)] public string pOutputFile;
 39           [MarshalAs(UnmanagedType.LPStr)] public string pDataType;
 40        }
 41        [DllImport("winspool.Drv", EntryPoint="OpenPrinterA", SetLastError=true, CharSet=CharSet.Ansi, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
 42        public static extern bool OpenPrinter([MarshalAs(UnmanagedType.LPStr)] string szPrinter, out IntPtr hPrinter, IntPtr pd);
 43  
 44        [DllImport("winspool.Drv", EntryPoint="ClosePrinter", SetLastError=true, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
 45        public static extern bool ClosePrinter(IntPtr hPrinter);
 46  
 47        [DllImport("winspool.Drv", EntryPoint="StartDocPrinterA", SetLastError=true, CharSet=CharSet.Ansi, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
 48        public static extern bool StartDocPrinter( IntPtr hPrinter, Int32 level,  [In, MarshalAs(UnmanagedType.LPStruct)] DOCINFOA di);
 49  
 50        [DllImport("winspool.Drv", EntryPoint="EndDocPrinter", SetLastError=true, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
 51        public static extern bool EndDocPrinter(IntPtr hPrinter);
 52  
 53        [DllImport("winspool.Drv", EntryPoint="StartPagePrinter", SetLastError=true, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
 54        public static extern bool StartPagePrinter(IntPtr hPrinter);
 55  
 56        [DllImport("winspool.Drv", EntryPoint="EndPagePrinter", SetLastError=true, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
 57        public static extern bool EndPagePrinter(IntPtr hPrinter);
 58  
 59        [DllImport("winspool.Drv", EntryPoint="WritePrinter", SetLastError=true, ExactSpelling=true, CallingConvention=CallingConvention.StdCall)]
 60        public static extern bool WritePrinter(IntPtr hPrinter, IntPtr pBytes, Int32 dwCount, out Int32 dwWritten );
 61  
 62        /*=================================================*/
 63        
 64        private IntPtr HandlePrinter;      
 65        private PrinterSettings ps;
 66                   
 67        public LPrinter()
 68        {
 69           HandlePrinter = IntPtr.Zero;
 70           ps = new PrinterSettings();         
 71        }
 72              
 73        public string PrinterName
 74        {
 75          get
 76          {
 77             return ps.PrinterName;
 78          }
 79          set
 80          {
 81             ps.PrinterName = value;
 82          }
 83        }
 84        
 85        public bool ChoosePrinter()
 86        {
 87           PrintDialog pd  = new PrintDialog();
 88           pd.PrinterSettings = ps;
 89           if(pd.ShowDialog()==DialogResult.OK)
 90           {
 91              ps = pd.PrinterSettings;
 92              return true;
 93           }
 94           else return false;
 95        }                  
 96         
 97        public bool Open(string DocName)
 98        {
 99           // see if printer is already open
100           if(HandlePrinter!=IntPtr.Zero) return false;
101  
102           // opens the printer
103           bool risp = OpenPrinter(ps.PrinterName,out HandlePrinter,IntPtr.Zero);
104           if(risp==false) return false;
105  
106           // starts a print job
107           DOCINFOA MyDocInfo = new DOCINFOA();
108           MyDocInfo.pDocName = DocName;
109           MyDocInfo.pOutputFile = null;
110           MyDocInfo.pDataType = "RAW";         
111           
112           if(StartDocPrinter(HandlePrinter, 1, MyDocInfo))
113           {
114              StartPagePrinter(HandlePrinter); //starts a page       
115              return true;
116           }
117           else return false;
118        }
119  
120        public bool Close()
121        {
122           if(HandlePrinter==IntPtr.Zero) return false;         
123           if(!EndPagePrinter(HandlePrinter)) return false;         
124           if(!EndDocPrinter(HandlePrinter)) return false;         
125           if(!ClosePrinter(HandlePrinter)) return false;         
126           HandlePrinter = IntPtr.Zero;
127           return true;
128        }
129         
130        public bool Print(string outputstring)
131        {
132           if(HandlePrinter==IntPtr.Zero) return false;
133                    
134           IntPtr buf = Marshal.StringToCoTaskMemAnsi(outputstring);
135                             
136           Int32 done = 0;
137           bool ok = WritePrinter(HandlePrinter,buf,outputstring.Length,out done);
138           
139           Marshal.FreeCoTaskMem(buf);         
140           
141           if(!ok) return false;
142           else return true;
143        }  
144        
145     }    

有人可以帮助我吗？