打印机 输出 不能用。，。为什么。，求大神。。 报外部引用错误

  public class PrintLab
        {
            [DllImport("WINPSK.dll")]
            public static extern int OpenPort(string printname);
            [DllImport("WINPSK.dll")]
            public static extern int PTK_SetPrintSpeed(uint px);
            [DllImport("WINPSK.dll")]
            public static extern int PTK_SetDarkness(uint id);
            [DllImport("WINPSK.dll")]
            public static extern int ClosePort();
            [DllImport("WINPSK.dll")]
            public static extern int PTK_PrintLabel(uint number, uint cpnumber);
            [DllImport("WINPSK.dll")]
            public static extern int PTK_DrawTextTrueTypeW
                                                (int x, int y, int FHeight,
                                                int FWidth, string FType,
                                                int Fspin, int FWeight,
                                                bool FItalic, bool FUnline,
                                                bool FStrikeOut,
                                                string id_name,
                                                string data);
            [DllImport("WINPSK.dll")]
            public static extern int PTK_DrawBarcode(uint px,
                                            uint py,
                                            uint pdirec,
                                            string pCode,
                                            uint pHorizontal,
                                            uint pVertical,
                                            uint pbright,
                                            char ptext,
                                            string pstr);
            [DllImport("WINPSK.dll")]
            public static extern int PTK_SetLabelHeight(uint lheight, uint gapH);
            [DllImport("WINPSK.dll")]
            public static extern int PTK_SetLabelWidth(uint lwidth);
            [DllImport("WINPSK.dll")]
            public static extern int PTK_ClearBuffer();
            [DllImport("WINPSK.dll")]
            public static extern int PTK_DrawRectangle(uint px, uint py, uint thickness, uint pEx, uint pEy);
            [DllImport("WINPSK.dll")]
            public static extern int PTK_DrawLineOr(uint px, uint py, uint pLength, uint pH);
            [DllImport("WINPSK.dll")]
            public static extern int PTK_SetPagePrintCount(uint number, uint cpnumber);
            [DllImport("WINPSK.dll")]
            public static extern int PTK_WritePrinter();
            [DllImport("WINPSK.dll")]
            public static extern int PTK_DrawBarcode();
            [DllImport("WINPSK.dll")]//打印QR二维码
            public static extern int PTK_DrawBar2D_QR(int x, int y, int w,  int v,int o,  int r,int m,  int g,int s, string pstr);
        }
        protected void Button1_Click(object sender, EventArgs e)
        { 
            string  a1="TY12021652897977";
            string  a2="93557673";            string value=a1+"                "+a2;
            //b200,200,QR,0,0,o0,r5,m2,g0,s0,"ABCabc12345"
            PrintLab.OpenPort("POSTEK C168 200s");//打开打印机端口
            PrintLab.PTK_ClearBuffer();//清空缓冲区
            PrintLab.PTK_SetPrintSpeed(3);//设置打印速度
            PrintLab.PTK_SetDarkness(8);//设置打印黑度
            PrintLab.PTK_SetLabelHeight(600, 200);//设置标签的高度和定位间隙\黑线\穿孔的高度
            PrintLab.PTK_SetLabelWidth(800);//设置标签的宽度
            for (int i = 1; i <= 2; i++)
            {
                //打印二维码 图形。
                //    PrintLab.PTK_DrawBar2D_QR(200, 200, 10, 10, 0, 1, 4, 0, 8, "aaa");
                                
                PrintLab.PTK_DrawTextTrueTypeW(200, 300, 40, 40, "宋体", 1, 400, false, true, true, "1", "你你你");//打印一行 TrueType Font文字
                PrintLab.PTK_DrawBarcode(100, 20, 0, "1", 3, 3, 80, 'N', "12345");//打印一个条码
                string name=null;
                //打印文本文字
                PrintLab.PTK_DrawBarcode(100, 20, 0, "1", 3, 3, 80, 'N', name);
                PrintLab.PTK_SetPagePrintCount(1, 1);//命令打印机执行打印工作
            }
            PrintLab.PTK_WritePrinter();
            PrintLab.ClosePort();//关闭打印机端口
            this.Label1.Text = "执行完毕！";
        }