Question

我不想覆盖XML文件中的数据我希望将旧数据和新数据保存在XML文件中。

我有三个班级：

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Email { get; set; }       

    public Person()
    {
    }

    public override string ToString()
    {
        return FirstName + " " +LastName + "\t" +Email;
    }
}

public class Student : Person
{
    public Student()
    {
    }
    public double AssessmentGrade { get; set; }
    public double AssignmentGrade { get; set; }

    public override string ToString()
    {
        return base.ToString() + "," +AssessmentGrade + "," + AssignmentGrade;
    }
}

public class Teacher : Person
{
    public int RoomNumber { get; set; }

    public override string ToString()
    {
        return base.ToString() + "," + RoomNumber;
    }
}

我还有一个类，我只调用PeronDB（Class）中的数据

public class Persons
{
    private List<Person> persons = null;

      public void Save()
    {
        PersonDB.SavePersons(persons);
    }
 }

我正在做的InPersonDB类将整个数据保存在XML文件中，但它会覆盖

public class PersonDB
{
    private const string path = @"..\..\Persons.xml";


    public static void SavePersons(List<Person> Persons)
    {
        XmlWriterSettings settings = new XmlWriterSettings();
        settings.Indent = true;
        settings.IndentChars = ("   ");

        XmlWriter xmlOut = XmlWriter.Create(path, settings);

        xmlOut.WriteStartDocument();
        xmlOut.WriteStartElement("Persons");

        foreach (Person person in Persons)
        {

                if (typeof(Student).IsInstanceOfType(person))
                {
                    AppendStudentInfo(person, xmlOut);
                }
                else if (typeof(Teacher).IsInstanceOfType(person))
                {
                    AppendTeacherInfo(person, xmlOut);
                }
                else
                {
                    AppendPersonInfo(person, xmlOut);
                }
        }

        xmlOut.WriteEndElement();
        xmlOut.Close();
    }

在我正在做的Form_Load事件中：

    Persons personList = null;

    private void FillPersonlstBox()
    {
        Person p;
        listBox1.Items.Clear();
        for (int i = 0; i < personList.Count; i++)
        {
            p = personList[i];
            listBox1.Items.Add(p.ToString());
        }
    }

    private void Save_Click(object sender, EventArgs e)
    {
        HandleChange(personList);
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        personList.Changed += new Persons.ChangeHandler(HandleChange);
    }

    private void HandleChange(Persons Persons)
    {
        Persons.Save();
        FillPersonlstBox();
    }

    private void Load_Click(object sender, EventArgs e)
    {
        personList.Changed += new Persons.ChangeHandler(HandleChange);
        personList.Fill();
        FillPersonlstBox();
    }

当我点击保存按钮时，它会覆盖删除旧数据的数据并保存新数据，即使我按下第一个加载按钮并加载数据，然后添加更多数据，之后我保存按下按钮重写..

Answer 1

您在PersonDB中的常量中有文件路径。而是将文件路径作为Save（）和SavePersons（）的参数。这样，您可以提示用户输入文件名并将其传入，或者让方法根据约定生成名称。

修改

以下是更改SavePersons签名以将路径作为参数包含的示例。

public static void SavePersons(List<Person> Persons, String path) { //your code }

将数据附加到现有xml文件

1 个答案: