C#Lpt端口打印类的操作浅析

C#LPT端口打印类的操作是什么呢？首先让我们看看什么是LPT端口（打印机专用）？LPT端口是一种增强了的双向并行传输接口，在USB接口出现以前是扫描仪，打印机最常用的接口。最高传输速度为1.5Mbps，设备容易安装及使用，但是速度比较慢，下面是C#LPT端口打印类的操作具体实例：

/// <summary>  
    /// LPTControl 的摘要说明，C#LPT端口打印类的操作  
    /// </summary>  
    public class LPTControls
    {
        public LPTControls() { }

        [StructLayout(LayoutKind.Sequential)]
        private struct OVERLAPPED
        {
            int Internal;
            int InternalHigh;
            int Offset;
            int OffSetHigh;
            int hEvent;
        }

        [DllImport("kernel32.dll")]
        private static extern int CreateFile(
         string lpFileName,
         uint dwDesiredAccess,
         int dwShareMode,
         int lpSecurityAttributes,
         int dwCreationDisposition,
         int dwFlagsAndAttributes,
         int hTemplateFile
         );

        [DllImport("kernel32.dll")]
        private static extern bool WriteFile(
         int hFile,
         byte[] lpBuffer,
         int nNumberOfBytesToWrite,
         ref int lpNumberOfBytesWritten,
         ref OVERLAPPED lpOverlapped
         );

        [DllImport("kernel32.dll")]
        private static extern bool CloseHandle(
         int hObject
         );

        //C#LPT端口打印类的操作  
        private int iHandle;
        public bool Open()
        {
            iHandle = CreateFile("lpt1", 0x40000000, 0, 0, 3, 0, 0);
            if (iHandle != -1)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        public bool Write(String Mystring)
        {
            if (iHandle != -1)
            {
                int i = 0;
                OVERLAPPED x = new OVERLAPPED();
                byte[] mybyte =
                System.Text.Encoding.Default.GetBytes(Mystring);
                return WriteFile(
                iHandle, mybyte, mybyte.Length, ref i, ref x);
            }
            else
            {
                throw new Exception("端口未打开!");
            }
        }

        public bool Close()
        {
            return CloseHandle(iHandle);
        }
    }