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)
