UPdating XML，获取“对象引用未设置为对象实例”。

Question

我试图更新XML文档中的3条数据，但得到了“对象引用未设置为对象实例”错误。这是我要更新的XML文件格式：

<?xml version="1.0" encoding="US-ASCII" standalone="true"?>
<ExportSettings xmlns="CompanyName" ExportName="Data Export" Dataset="TestName">
  <General>
     <AsOfDate>03/31/15</AsOfDate>
     <PriceDate>03/31/16</PriceDate>  
  </General>
  <Source>
      <Set>Set Name</Set>
  </Source>
</ExportSettings>

这是抛出错误的C#代码：

    private void btnUpdate_Click(object sender, EventArgs e)
    {
        try
        {
            {
                string strAsOfDate = dateTimePickerAsOfDate.Text;
                string strPriceDate = dateTimePickerPriceDate.Text;
                string strSetName = txtboxSet.Text;

                XmlDocument doc = new XmlDocument();
                doc.Load(strXMLfilepath);
                XmlNode General;
                XmlNode root = doc.DocumentElement;
                General = root.SelectSingleNode("/ExportSettings/General");
                General["AsOfDate"].InnerText = strAsOfDate;
                General["PriceDate"].InnerText = strPriceDate;
                XmlNode Source;
                Source = root.SelectSingleNode("/ExportSettings/Source");
                Source["Set"].InnerText = strSetName;
                doc.Save(strXMLfilepath);

            }
        }
        catch (System.Exception excep)
        {
            MessageBox.Show(excep.Message);
        }
    }

有人能看到问题吗？我不太熟悉XML的更新，所以这里可能有一些基本的错误。

Answer 1

我已经在本地调试了它，正如Pawel所建议的，您需要对名称空间进行一些更改：

private void btnUpdate_Click(object sender, EventArgs e)
{
    try
    {
        {
            string strAsOfDate = dateTimePickerAsOfDate.Text;
            string strPriceDate = dateTimePickerPriceDate.Text;
            string strSetName = txtboxSet.Text;

            XmlDocument doc = new XmlDocument();
            doc.Load(strXMLfilepath);

            XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
            nsmgr.AddNamespace("ab", "CompanyName");

            XmlNode General;
            XmlNode root = doc.DocumentElement;
            General = root.SelectSingleNode("//ab:General", nsmgr);
            General["AsOfDate"].InnerText = strAsOfDate;
            General["PriceDate"].InnerText = strPriceDate;

            doc.Save(strXMLfilepath);
        }
    }
    catch (System.Exception excep)
    {
        MessageBox.Show(excep.Message);
    }
}

希望这能有所帮助。