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..
答案 0 :(得分: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
}