C#调用codesoft模板打印条码

C#初学者，因近期要用到条码打印，便从网上找了些资料来学习，但在实际支行程序却得到“未将对象引用设置到对象的实例”。附件是源代码和打印模板，请高手指点一二，谢谢！



using System;
using System.Collections.Generic;
using
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using LabelManager2;//已安装好CodeSoft 6.0,并在“引用”中引用了Lppx2.tlb

namespace WindowsFormsApplication10
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            ApplicationClass lbl = new ApplicationClass();

            try
            {
                lbl.Documents.Open(@"D:\222.Lab", false);// 调用设计好的label文件
                Document doc = lbl.ActiveDocument;
                doc.Variables.FormVariables.Item("Var0").Value = txtContent1.Text.Trim(); //给参数传值
                doc.Variables.FormVariables.Item("Var1").Value = txtContent2.Text.Trim(); //给参数传值

                int Num = Convert.ToInt32(txtQuentity.Text);        //打印数量
                doc.PrintDocument(Num);                             //打印
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                lbl.Quit();                                         //退出
            }
        }
    }
}