用XmlNode.Attributes填充文本框

我有Data.xml:

<?xml version="1.0" encoding="utf-8" ?>
<data>
<album>
    <slide title="Autum Leaves"
        description="Leaves from the fall of 1986"
        source="images/Autumn Leaves.jpg"
        thumbnail="images/Autumn Leaves_thumb.jpg" />
    <slide title="Creek"
        description="Creek in Alaska"
        source="images/Creek.jpg"
        thumbnail="images/Creek_thumb.jpg" />
</album>
</data>

我希望能够通过GridView(添加了“Select”列)编辑每个幻灯片节点的属性,到目前为止,我已经:

protected void GridView1_SelectedIndexChanged(object sender, EventArgs e)
{
    int selectedIndex = GridView1.SelectedIndex;
    LoadXmlData(selectedIndex);
}

private void LoadXmlData(int selectedIndex)
{
    XmlDocument xmldoc = new XmlDocument();
    xmldoc.Load(MapPath(@"..\photo_gallery\Data.xml"));
    XmlNodeList nodelist = xmldoc.DocumentElement.ChildNodes;
    XmlNode xmlnode = nodelist.Item(selectedIndex);
    titleTextBox.Text = xmlnode.Attributes["title"].InnerText;
    descriptionTextBox.Text = xmlnode.Attributes["description"].InnerText;
    sourceTextBox.Text = xmlnode.Attributes["source"].InnerText;
    thumbTextBox.Text = xmlnode.Attributes["thumbnail"].InnerText;
}

LoadXmlData的代码只是我的猜测——我对用这种方式处理xml还不熟悉。我希望用户从gridview中选择行,然后填充一组文本框,每个幻灯片都有属性,以便更新回Data.xml文件。

我得到的错误是对象引用没有设置为一个对象的实例“在:titleTextBox.Text=xmlnode.Attributes[“@title”].InnerText;

所以我没有到达幻灯片节点的属性“title”。谢谢你的建议。