c#，lambda表达式，错误在哪里？

我有这个方法

    public static List<Contact> Load(string filename)
    {
        if (!File.Exists(filename))
        {
            throw new FileNotFoundException("Data file could not be found", filename);

        }
        var contacts = 
            System.Xml.Linq.XDocument.Load(filename).Root.Elements("Contact").Select
            (
                x => new Contact() { //errors out here, XXXXXX
                            FirstName = (string)x.Element("FirstName"),
                            LastName = (string)x.Element("LastName"),
                            Email = (string)x.Element("Email")
                         }
            );
        return contacts.ToList();// is this line correct?, it should return List...
    }

---

在标有“XXXXXX”的行上，我应该如何更改行以使其工作？

您的

联系人

类的构造函数需要三个参数-

firstName

，

lastName

和

email

-但是您正在尝试调用没有参数的构造函数，然后尝试使用设置属性

要修复它，您需要将三个参数传递到构造函数本身：

x => new Contact(
    (string)x.Element("FirstName"),
    (string)x.Element("LastName"),
    (string)x.Element("Email"));

---

我想你失去了一个联系中的公共构造函数

public class Contact
{
    public Contact() {}

    public Contact(string firstName, string lastName, string email) {
        FirstName = firstName;
        LastName = lastName;
        Email = email;
    }

    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Email { get; set; }
    public string PhoneNumber { get; set; }
    public string Address { get; set; }
}

或者只使用现有的构造函数

x => new Contact(
    (string)x.Element("FirstName"),
    (string)x.Element("LastName"),
    (string)x.Element("Email"));

public class Contact
{
    public Contact() {}

    public Contact(string firstName, string lastName, string email) {
        FirstName = firstName;
        LastName = lastName;
        Email = email;
    }

    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Email { get; set; }
    public string PhoneNumber { get; set; }
    public string Address { get; set; }
}