c＃SSIS - 未将对象引用设置为对象的实例

Question

我正在研究SSIS包（这对我来说是新的）。我使用脚本组件作为源，我使用ReadOnlyVariable（VarPackagePath）并为其分配一个值＆＃39; C：\ Development \ SSISProjects \ VS2012 \ GetErrorColumn \ GetErrorColumn \ Package.dtsx＆＃39;这是项目的位置。 我使用的脚本是获取发生错误的relavent列。 我关注的链接：http://www.techbrothersit.com/2013/12/ssis-how-to-get-error-column-name-in.html

我调试了我的c＃代码，我在这一行收到错误：

TaskName = ExecutableNode.SelectSingleNode("DTS:Property[@DTS:Name='ObjectName']", NameSpcMgr).InnerText;

错误是：'Object reference not set to an instance of an object'。

我的C＃代码：

 public override void CreateNewOutputRows()
{
    /*
      Add rows by calling the AddRow method on the member variable named "<Output Name>Buffer".
      For example, call MyOutputBuffer.AddRow() if your output was named "MyOutput".
    */
    //Declare Variables
    String TaskName;
    String ColName;
    Int32 ColLineageID;
    String ColKey;

    //Read the Package File
    XmlDocument PackageFile = new XmlDocument();
    PackageFile.Load(Variables.VarPackagePath);

    //Create Hash Table 
    Hashtable ColKeyTable = new Hashtable();


    XmlNamespaceManager NameSpcMgr = new XmlNamespaceManager(PackageFile.NameTable);
    NameSpcMgr.AddNamespace("DTS", "www.microsoft.com/SqlServer/Dts");

    foreach (XmlNode childnode in PackageFile.SelectNodes("//*[@lineageId != '' and @name != '']"))
    {


        XmlNode ExecutableNode = childnode.SelectSingleNode("ancestor::DTS:Executable[1]", NameSpcMgr);
        TaskName = ExecutableNode.SelectSingleNode("DTS:Property[@DTS:Name='ObjectName']", NameSpcMgr).InnerText;
        ColName = childnode.Attributes["name"].Value;
        ColLineageID = Convert.ToInt32(childnode.Attributes["lineageId"].Value);
        ColKey = TaskName + ColName + ColLineageID;
        if (!ColKeyTable.ContainsKey(ColKey))
        {
            ColKeyTable.Add(ColKey, DBNull.Value);

            Output0Buffer.AddRow();
            Output0Buffer.ColLineageID = ColLineageID;
            Output0Buffer.ColName = ColName;
            Output0Buffer.TaskName = TaskName;
        }
    }
}

请提供任何帮助/建议。