在C＃中找到xml元素

Question

我正在嘗試在市民列表中查找特定元素，但結果始終為null。 提前致謝！ 這是我正在嘗試的代碼：

string filepath = "citizens.xml";
if (!File.Exists(filepath))
{
    CitizensList list = new CitizensList();
    Serializer.SerializeObject(filepath, list);
}

CitizensList citizens = Serializer.DeSerializeObject(filepath);
Console.WriteLine("The File {0} has this data", filepath);
citizens.print();


Console.WriteLine("Chose the name of the citizen from the console");        
string name = Console.ReadLine();

CitizensList search = new CitizensList();
var matching = search.Citizen.Find(p => p.FirstName==(name));
if (matching == null)
{
    Console.WriteLine("The Citizen doesn't exists.");
}
else
{
    Serializer.SerializeObject(filepath, citizens);
    citizens = Serializer.DeSerializeObject(filepath);
    search.print();
}

這是我的代碼，用於在xml文件中正確地插入數據：

Console.WriteLine("Insert the data of the citizen");
                        Console.WriteLine("Name:");
                        string nm = Console.ReadLine();
                        Console.WriteLine("Surname:");
                        string sn = Console.ReadLine();
                        Console.WriteLine("Email:");
                        string email = Console.ReadLine();
                        Console.WriteLine("Phone:");
                        string no = Console.ReadLine();
                        Citizens citizen = new Citizens();
                        if (citizens.Citizen.Count == 0)
                            citizen.Id = 1;
                        else
                            citizen.Id = Convert.ToInt32(citizens.Citizen.Last<Citizens>().Id) + 1;
                        citizen.FirstName = nm;
                        citizen.Lastname = sn;
                        citizen.Email = email;
                        citizen.PhoneNr = no;
                        citizens.Citizen.Add(citizen);

                        Serializer.SerializeObject(filepath, citizens);
                        citizens = Serializer.DeSerializeObject(filepath);
                        citizens.print();

Answer 1

您正在search中search ，這是一個新創建的（只能假設） 空列表。

var matching = search.Citizen.Find(p => p.FirstName==(name));

您應該在搜索citizens ，您的列表從文件中讀取：

var matching = citizens.Citizen.Find(p => p.FirstName == name);