在使用winform编写自动打印服务的过程中，发现只要进行了打印命令的调用，文档就会进入到打印等待队列，如果打印机无法正常工作，则会影响到相关业务数据的正确转换，所以需要检查打印机的状态来保障每次打印时打印机处于空闲状态，打印时队列中也只能有一个文档，本文是通过引用System.Management来实现对打印机状态的查询

打印机状态获取

        enum PrinterStatus
        {
            其他 = 1,
            未知 = 2,
            空闲 = 3,
            打印 = 4,
            预热 = 5,
            停止打印 = 6,
            脱机 = 7,
        }

        /// <summary>
        /// 获取打印机的当前状态
        /// </summary>
        /// <param name="PrinterDevice">打印机设备名称</param>
        /// <returns>打印机状态</returns>
        private static PrinterStatus GetPrinterPrinterStatus(string PrinterDevice)
        {
            PrinterStatus ret = 0;
            string path = @"win32_printer.DeviceId='" + PrinterDevice + "'";
            ManagementObject printer = new ManagementObject(path);
            printer.Get();
            ret = (PrinterStatus)Convert.ToInt32(printer.Properties["PrinterStatus"].Value);
            return ret;
        }

打印机脱机检查

        public static bool CheckPrinter(string BindPrintName)
        {
            ManagementScope scope = new ManagementScope(@"\root\cimv2");
            scope.Connect();

            // Select Printers from WMI Object Collections
            ManagementObjectSearcher searcher = new ManagementObjectSearcher("SELECT * FROM Win32_Printer");

            string printerName = "";
            foreach (ManagementObject printer in searcher.Get())
            {
                printerName = printer["Name"].ToString().ToLower();
                if (printerName.IndexOf(BindPrintName.ToLower()) > -1)
                {
                    //foreach (var property in printer.Properties)
                    //{
                    //    LogUtil.WriteLog(property.Name + ":" + property.Value);
                    //}
                    if (printer["WorkOffline"].ToString().ToLower().Equals("true"))
                    {
                        return false;
                    }
                    else
                    {
                        return true;
                    }
                }
            }
            return false;
        }

打印机阻塞队列实现

这里主要是通过一个while循环来不停的获取打印机的状态，空闲时才会进行下一次打印，通过两个标志位来配合轮询的外部介入退出

FinishWait标志位是任务内部的标识，如果打印机检查到了错误状态则进行轮询退出

GlobalInfo.IsGlobalExist标志位是程序全局标识，如果界面上通知用户等待时间过长，可以进行人工手动干预退出

                    //检查打印机状态
                    if (!CheckPrinter(PrintName))
                    {
                        throw new PrintCheckException("打印机处于脱机状态");
                    }
                    PrinterStatus State = GetPrinterPrinterStatus(PrintName);
                    if (State == PrinterStatus.空闲)
                    {

                    }
                    else if (State == PrinterStatus.打印 || State == PrinterStatus.预热)
                    {
                        //正在打印/预热时循环去查询打印机状态，如果变成了就绪就开始打印
                        while (State != PrinterStatus.空闲 && !FinishWait && !GlobalInfo.IsGlobalExist)
                        {
                            State = GetPrinterPrinterStatus(PrintName);
                            if (!CheckPrinter(PrintName))
                            {
                                FinishWait = true;
                                throw new PrintCheckException("打印机处于脱机状态");
                            }
                            if (State == PrinterStatus.打印 || State == PrinterStatus.预热 || State == PrinterStatus.空闲)
                            {
                                if (State == PrinterStatus.空闲)
                                {

                                    FinishWait = true;
                                }
                            }
                            else
                            {
                                FinishWait = true;
                                throw new PrintCheckException("打印机状态错误，当前状态：" + State.ToString());
                            }
                        }