最近需要做一个打印的功能，于是在网上找到了这么一个方法。

　　[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
    public class DOCINFOA
        [MarshalAs(UnmanagedType.LPStr)]
        public string pDocName;
        [MarshalAs(UnmanagedType.LPStr)]
        public string pOutputFile;
        [MarshalAs(UnmanagedType.LPStr)]
        public string pDataType;
    public class PrintCode
        [DllImport("winspool.Drv", EntryPoint = "OpenPrinterA", SetLastError = true, CharSet = CharSet.Ansi, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
        public static extern bool OpenPrinter([MarshalAs(UnmanagedType.LPStr)] string szPrinter, out IntPtr hPrinter, IntPtr pd);
        [DllImport("winspool.Drv", EntryPoint = "ClosePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
        public static extern bool ClosePrinter(IntPtr hPrinter);
        [DllImport("winspool.Drv", EntryPoint = "StartDocPrinterA", SetLastError = true, CharSet = CharSet.Ansi, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
        public static extern bool StartDocPrinter(IntPtr hPrinter, Int32 level, [In, MarshalAs(UnmanagedType.LPStruct)] DOCINFOA di);
        [DllImport("winspool.Drv", EntryPoint = "EndDocPrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
        public static extern bool EndDocPrinter(IntPtr hPrinter);
        [DllImport("winspool.Drv", EntryPoint = "StartPagePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
        public static extern bool StartPagePrinter(IntPtr hPrinter);
        [DllImport("winspool.Drv", EntryPoint = "EndPagePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
        public static extern bool EndPagePrinter(IntPtr hPrinter);
        [DllImport("winspool.Drv", EntryPoint = "WritePrinter", SetLastError = true, ExactSpelling = true, CallingConvention = CallingConvention.StdCall)]
        public static extern bool WritePrinter(IntPtr hPrinter, IntPtr pBytes, Int32 dwCount, out Int32 dwWritten);
        /// <summary>
        /// 该方法把非托管内存中的字节数组发送到打印机的打印队列
        /// </summary>
        /// <param name="szPrinterName">打印机名称</param>
        /// <param name="pBytes">非托管内存指针</param>
        /// <param name="dwCount">字节数</param>
        /// <returns>成功返回true，失败时为false</returns>
        public static bool SendBytesToPrinter(string szPrinterName, IntPtr pBytes, Int32 dwCount)
            Int32 dwError = 0, dwWritten = 0;
            IntPtr hPrinter = new IntPtr(0);
            DOCINFOA di = new DOCINFOA();
            bool bSuccess = false;
            di.pDocName = "My C#.NET RAW Document";
            di.pDataType = "RAW";
                // 打开打印机
                if (OpenPrinter(szPrinterName.Normalize(), out hPrinter, IntPtr.Zero))
                    // 启动文档打印
                    if (StartDocPrinter(hPrinter, 1, di))
                        // 开始打印
                        if (StartPagePrinter(hPrinter))
                            // 向打印机输出字节  
                            bSuccess = WritePrinter(hPrinter, pBytes, dwCount, out dwWritten);
                            EndPagePrinter(hPrinter);
                        EndDocPrinter(hPrinter);
                    ClosePrinter(hPrinter);
                if (bSuccess == false)
                    dwError = Marshal.GetLastWin32Error();
            catch (Win32Exception ex)
                WriteLog(ex.Message);
                bSuccess = false;
            return bSuccess;
        /// <summary>
        /// 发送文件到打印机方法
        /// </summary>
        /// <param name="szPrinterName">打印机名称</param>
        /// <param name="szFileName">打印文件的路径</param>
        /// <returns></returns>
        public static bool SendFileToPrinter(string szPrinterName, string szFileName)
            bool bSuccess = false;
                // 打开文件  
                FileStream fs = new FileStream(szFileName, FileMode.Open);
                // 将文件内容读作二进制
                BinaryReader br = new BinaryReader(fs);
                // 定义字节数组
                Byte[] bytes = new Byte[fs.Length];
                // 非托管指针  
                IntPtr pUnmanagedBytes = new IntPtr(0);
                int nLength;
                nLength = Convert.ToInt32(fs.Length);
                // 读取文件内容到字节数组
                bytes = br.ReadBytes(nLength);
                // 为这些字节分配一些非托管内存
                pUnmanagedBytes = Marshal.AllocCoTaskMem(nLength);
                // 将托管字节数组复制到非托管内存指针
                Marshal.Copy(bytes, 0, pUnmanagedBytes, nLength);
                // 将非托管字节发送到打印机
                bSuccess = SendBytesToPrinter(szPrinterName, pUnmanagedBytes, nLength);
                // 释放先前分配的非托管内存
                Marshal.FreeCoTaskMem(pUnmanagedBytes);
                fs.Close();
                fs.Dispose();
            catch (Win32Exception ex)
                WriteLog(ex.Message);
                bSuccess = false;
            return bSuccess;
        /// <summary>
        /// 将字符串发送到打印机方法
        /// </summary>
        /// <param name="szPrinterName">打印机名称</param>
        /// <param name="szString">打印的字符串</param>
        /// <returns></returns>
        public static bool SendStringToPrinter(string szPrinterName, string szString)
            bool flag = false;
                IntPtr pBytes;
                Int32 dwCount;
                // 获取字符串长度  
                dwCount = szString.Length;
                // 将字符串复制到非托管 COM 任务分配的内存非托管内存块，并转换为 ANSI 文本
                pBytes = Marshal.StringToCoTaskMemAnsi(szString);
                // 将已转换的 ANSI 字符串发送到打印机
                flag = SendBytesToPrinter(szPrinterName, pBytes, dwCount);
                // 释放先前分配的非托管内存
                Marshal.FreeCoTaskMem(pBytes);
            catch (Win32Exception ex)
                WriteLog(ex.Message);
                flag = false;
            return flag;
        /// <summary>
        /// 写入日志方法
        /// </summary>
        /// <param name="msg">记录信息</param>
        public static void WriteLog(string msg)
            string str = string.Empty;
            string path = AppDomain.CurrentDomain.BaseDirectory + "log\\" + DateTime.Now.ToString("yyyy-MM-dd") + ".txt";
            FileStream filestream = new FileStream(path, FileMode.OpenOrCreate);
            str += "************" + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + "************\r\n";
            str += msg;
            str += "************" + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + "************\r\n";
            FileStream fs = new FileStream(path, FileMode.Append);
            StreamWriter sw = new StreamWriter(fs, System.Text.Encoding.Default);
            sw.WriteLine(str);
            sw.Flush();
            sw.Close();
            sw.Dispose();
            fs.Close();
            fs.Dispose();
以上就是全部代码了，调用就很简单了，方法如下：
private void Print_Click(object sender, EventArgs e)
            //打印文件的路径，该方法获取到的文件路径在应用程序 bin\Debug\ 目录下，所以 ../../ 向上两级目录
            string fileName = AppDomain.CurrentDomain.BaseDirectory + @"../../File/demo.txt";
            if (PrintCode.SendFileToPrinter("PrinterName", fileName))
                MessageBox.Show("文件已成功发送至打印队列！","提示信息");