C#调用CodeSoft打印条码 ,未将对象引用设置到对象的实例怎么解决?

Question

public bool PrintMAC(DataTable dtb, string barcode, string Prefix, string SerNum, int ptnum, string model, out string error)
{
Kill("lppa");
model = AppDomain.CurrentDomain.BaseDirectory + model;//取当前应用程序域运行的目录
LabelManager2.ApplicationClass PrintApp = new LabelManager2.ApplicationClass();

    try
    {
        LabelManager2.Document PrintDoc = PrintApp.ActiveDocument;
        PrintDoc = PrintApp.Documents.Open(model, false);
        if (PrintDoc == null)
        {
            error = "模版未找到";
            return false;
        }

        if (!string.IsNullOrEmpty(barcode))
        {
            PrintDoc.Variables.Counters.Item(barcode).Prefix = Prefix;
            PrintDoc.Variables.Counters.Item(barcode).Value = SerNum;
        }

        for (int j = 0; j < dtb.Rows.Count; j++) //行
        {
            for (int i = 0; i < dtb.Columns.Count; i++) //列
            {
                try
                {
                    string col = dtb.Columns[i].ColumnName.ToString();
                    string txt = dtb.Rows[j][col].ToString();
                    PrintDoc.Variables.FormVariables.Item(col).Value = txt;
                }
                catch (Exception ex)
                {
                    error = ex.Message;
                    return false;
                }
            }
            PrintDoc.PrintDocument(1);

        }
        error = "打印成功";
        return true;

    }
    catch (Exception ex)
    {
        error = ex.Message;
        return false;
    }
    finally
    {
        PrintApp.Documents.CloseAll(false);
        PrintApp.Quit();
    }

}

Answer 1

https://zhidao.baidu.com/question/391172326609270565.html