急，System.NullReferenceException: 未将对象引用设置到对象的实例

DongloveRen 2009-06-07 07:56:00

我在做向一个xml中插入记录的程序，出错！
xml代码：

<?xml version="1.0" encoding="UTF-8"?>

<StudentInfoManagementSystem>

	<StudentInfos>

		<StudentInfo>

			<StudentName>dong</StudentName>

			<StudentNum>666666</StudentNum>

			<StudentGender>man</StudentGender>

			<StudentAddress>Tonghai</StudentAddress>

			<StudentBirth>12345678</StudentBirth>

			<StudentTel>12345678912</StudentTel>

			<DepartNum>08</DepartNum>

			<ClassNum>062</ClassNum>

			<ScoreInfos>

				<ScoreInfo>

					<CourseNum>11111111</CourseNum>

					<Score>88</Score>

				</ScoreInfo>

			</ScoreInfos>

		</StudentInfo>

	</StudentInfos>

</StudentInfoManagementSystem>

程序代码：



 public partial class StudentManagementSystem : Form

    {

        public static XmlDocument myXmlDoc = new XmlDocument();

        public StudentManagementSystem()

        {

            InitializeComponent();

        }



        private void addButton_Click(object sender, EventArgs e)

        {

            string filePath = Application.StartupPath + "../../../XmlDoc/StudentManagementSystem.xml";



            myXmlDoc.Load(filePath);

            string name = nameTextBox.Text;

            string num = numberTextBox.Text;

            string sex = sexTextBox.Text;

            string address = addressTextBox.Text;

            string birthday = birthTextBox.Text;

            

            XmlNode myNode = myXmlDoc.SelectSingleNode("StudentInfos");



            XmlElement myXmlElementNode = myXmlDoc.CreateElement("StudentInfo");

            //XmlNode myXmlElementNode = myXmlDoc.CreateNode



            XmlElement myXmlElemrntName = myXmlDoc.CreateElement("StudentName");

            myXmlElemrntName.InnerText = name;

            XmlElement myXmlElementNum = myXmlDoc.CreateElement("StudentNum");

            myXmlElementNum.InnerText = num;

            XmlElement myXmlElementSex = myXmlDoc.CreateElement("StudentGender");

            myXmlElementSex.InnerText = sex;

            XmlElement myXmlElementAddress = myXmlDoc.CreateElement("StudentAddress");

            myXmlElementAddress.InnerText = address;

            XmlElement myXmlElementBirthday = myXmlDoc.CreateElement("StudentBirth");

            myXmlElementBirthday.InnerText = birthday;



            myXmlElementNode.AppendChild(myXmlElemrntName);

            myXmlElementNode.AppendChild(myXmlElementNum);

            myXmlElementNode.AppendChild(myXmlElementSex);

            myXmlElementNode.AppendChild(myXmlElementAddress);

            myXmlElementNode.AppendChild(myXmlElementBirthday);

//////////////////////////////////////////////////////////////////

////////////////////////55就是下面这/////////////////////////////////////////

            myNode.AppendChild(myXmlElementNode);

//////////////////////////////////////////////////////////////////////////

            myXmlDoc.Save(filePath);

            MessageBox.Show("添加成功！");

        }

    }

错误：
************* 异常文本 **************
System.NullReferenceException: 未将对象引用设置到对象的实例。
在 StudentManagementSystem.StudentManagementSystem.addButton_Click(Object sender, EventArgs e) 位置 D:\\StudentManagementSystem\Form1.cs:行号 55
在 System.Windows.Forms.Control.OnClick(EventArgs e)
在 System.Windows.Forms.Button.OnClick(EventArgs e)
在 System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
在 System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
在 System.Windows.Forms.Control.WndProc(Message& m)
在 System.Windows.Forms.ButtonBase.WndProc(Message& m)
在 System.Windows.Forms.Button.WndProc(Message& m)
在 System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
在 System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
在 System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

...全文

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皓月明 2009-06-08

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问题解决啦，要从根节点找起

wuyq11 2009-06-07

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XmlDocument xmlDoc=new XmlDocument();
xmlDoc.Load(Server.MapPath("data.xml"));
XmlNode root=xmlDoc.SelectSingleNode("/StudentInfoManagementSystem/StudentInfos");
XmlElement xe1=xmlDoc.CreateElement("StudentInfo");

XmlElement xesub1=xmlDoc.CreateElement("StudentName");
xesub1.InnerText="";
xe1.AppendChild(xesub1);
XmlElement xesub2=xmlDoc.CreateElement("StudentNum");
xesub2.InnerText="";
xe1.AppendChild(xesub2);
XmlElement xesub3=xmlDoc.CreateElement("StudentGender");
xesub3.InnerText="";
xe1.AppendChild(xesub3);

root.AppendChild(xe1);
xmlDoc.Save ( Server.MapPath("data.xml") );

DongloveRen 2009-06-07

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问题已经解决，谢谢！

冷月孤峰 2009-06-07

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XmlNode myNode = myXmlDoc.SelectSingleNode("StudentInfos");改成：
XmlNode myNode = myXmlDoc.SelectSingleNode("/StudentInfoManagementSystem/StudentInfos");

XIAODONGXIAN 2009-06-07