可能重复：
我想从 XML 文件加载数据并显示在列表框中？
我有一个三类：
首先是人：
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;
}
}
二是：
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;
}
}
第三是：
public class Teacher:Person
{
public int RoomNumber
{
get;
set;
}
public override string ToString()
{
return base.ToString() + "," + RoomNumber;
}
}
我还有一门课，我只是从 PeronDB （类）中调用数据
public class Persons
{
private List<Person> persons = null;
public void Fill()
{
persons = PersonDB.GetPersons();
}
}
InPersonDB 类如果它的 Student 节点然后读取数据，如果它的 Teacher 节点也读取数据并且如果它 Person 它也读取数据，我正在做。
public class PersonDB
{
private const string path = @"..\..\Persons.xml";
public static List<Person> GetPersons()
{
List<Person> persons = new List<Person>();
XmlReaderSettings settings = new XmlReaderSettings();
settings.IgnoreWhitespace = true;
settings.IgnoreComments = true;
XmlReader xmlIn = XmlReader.Create(path, settings);
if (xmlIn.ReadToDescendant("Student"))
{
do
{
Person person = new Person();
Student student = (Student)person;
xmlIn.ReadStartElement("Student");
student.FirstName = xmlIn.ReadElementContentAsString();
student.LastName = xmlIn.ReadElementContentAsString();
student.Email = xmlIn.ReadElementContentAsString();
student.AssessmentGrade = xmlIn.ReadElementContentAsInt();
student.AssignmentGrade = xmlIn.ReadElementContentAsInt();
persons.Add(student);
} while (xmlIn.ReadToNextSibling("Student"));
}
else if (xmlIn.ReadToDescendant("Teacher"))
{
do
{
Person person = new Person();
Teacher teacher = (Teacher)person;
xmlIn.ReadStartElement("Teacher");
teacher.FirstName = xmlIn.ReadElementContentAsString();
teacher.LastName = xmlIn.ReadElementContentAsString();
teacher.Email = xmlIn.ReadElementContentAsString();
teacher.RoomNumber = xmlIn.ReadElementContentAsInt();
persons.Add(teacher);
} while (xmlIn.ReadToNextSibling("Teacher"));
}
if (xmlIn.ReadToDescendant("Person"))
{
do
{
Person person = new Person();
xmlIn.ReadStartElement("Person");
person.FirstName = xmlIn.ReadElementContentAsString();
person.LastName = xmlIn.ReadElementContentAsString();
person.Email = xmlIn.ReadElementContentAsString();
persons.Add(person);
} while (xmlIn.ReadToNextSibling("Person"));
}
xmlIn.Close();
return persons;
}
}
在表单加载中我正在做：
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 Load_Click(object sender, EventArgs e)
{
personList.Changed += new Persons.ChangeHandler(HandleChange);
personList.Fill();
FillPersonlstBox();
}
它告诉我“{Unable to cast object of type 'Collection.Person' to type 'Collection.Student'。”}这个错误:( System.InvalidCastException 它在 PersonDB 类中显示这个错误。请大家帮我如何解决它？