使用 first/last 名称和年龄 C# 对名称列表进行排序

Question

我想首先按年龄对列表中的名字进行排序（到目前为止我已经这样做了），但我想知道如何在打印到新文件之前再次按姓氏对这些名字进行排序。例如，如果我有 5 个 20 岁的人，姓氏不同，我如何确保这 5 个人按字母顺序升序排列？

class Person : IComparable
{
    string vorname;
    string nachname;
    int age;

    public Person(string vorname, string nachname, int age)
    {
        this.age = age;
        this.nachname = nachname;
        this.vorname = vorname;
    }

    public int CompareTo(object obj)
    {
        Person other = (Person)obj;
        int a = this.age - other.age;

        if (a != 0)
        {
            return -a;
        }
        else
        {
            return age.CompareTo(other.age);
        }
    }

    public override string ToString()
    {
        return vorname + " " + nachname + "\t" + age;
    }        
}

class Program
{
    static void Main(string[] args)
    {
        Person[] peeps = new Person[20];

        try
        {
            StreamReader sr = new StreamReader("inputNames.txt");

            int count = 0;

            while (!sr.EndOfStream)
            {
                string data = sr.ReadLine();
                Console.WriteLine();
                string[] info = data.Split(',');
                peeps[count] = new Person(info[0], info[1], int.Parse(info[2]));

                count++;
            }
            Array.Sort(peeps);
            sr.Close();
        }
        catch(FileNotFoundException e)
        {
            Console.WriteLine(e.Message);
        }

        StreamWriter sw = new StreamWriter("outputNames.txt");

        Console.WriteLine();
        foreach (Person p in peeps)
        {
            Console.WriteLine(p);
            sw.WriteLine(p);
        }
        sw.Close();
    }
}

Answer 1

Linq 是你的朋友。您可以在 1 行中重写所有代码：

peeps.OrderBy(x => x.Age).ThenBy(x => x.LastName);

仅此而已:)。您可以摆脱所有 IComparable 垃圾，那是老派。

编辑：对于 IComparable，您可以：

    public int CompareTo(object obj)
    {
        Person other = (Person)obj;

        if (age < other.age)
            return -1;

        if (String.Compare(vorname, other.vorname) < 0)
            return -1;

        return 1;
    }

似乎适合我的快速测试，但要多测试一下:)。

Answer 2

您可以使用 Linq：

 people.OrderBy(person => person.age)
     .ThenBy(person => person.LastName);

Answer 3

有点过时，但仍然如此。您可以使用 Comparers 并在以后根据需要灵活使用它们：

    public class AgeComparer: Comparer<Person> 
    {
        public override int Compare(Person x, Person y)
        {   

           return x.Age.CompareTo(y.Age);      
        }    
    }
    public class LastNameThenAgeComparer: Comparer<Person> 
    {
        public override int Compare(Person x, Person y)
        {       
            if (x.LastName.CompareTo(y.LastName) != 0)
            {
               return x.LastName.CompareTo(y.LastName);
            }
            else (x.Age.CompareTo(y.Age) != 0)
            {
               return x.Age.CompareTo(y.Age);
            }    
        }    
    }
//// other types of comparers

用法：

personList.Sort(new LastNameThenAgeComparer());

Answer 4

LINQ + 扩展方法

class Program
{
    static void Main(string[] args)
    {
        try
        {
            "inputNames.txt".ReadFileAsLines()
                            .Select(l => l.Split(','))
                            .Select(l => new Person
                            {
                                vorname = l[0],
                                nachname = l[1],
                                age = int.Parse(l[2]),
                            })
                            .OrderBy(p => p.age).ThenBy(p => p.nachname)
                            .WriteAsLinesTo("outputNames.txt");
        }
        catch (Exception e)
        {
            Console.Error.WriteLine(e.Message);
        }
    }
}
public class Person
{
    public string vorname { get; set; }
    public string nachname { get; set; }
    public int age { get; set; }

    public override string ToString()
    {
        return string.Format("{0} {1}\t{2}", this.vorname, this.nachname, this.age);
    }
}
public static class ToolsEx
{
    public static IEnumerable<string> ReadFileAsLines(this string filename)
    {
        using (var reader = new StreamReader(filename))
            while (!reader.EndOfStream)
                yield return reader.ReadLine();
    }
    public static void WriteAsLinesTo(this IEnumerable lines, string filename)
    {
        using (var writer = new StreamWriter(filename))
            foreach (var line in lines)
                writer.WriteLine(line);
    }
}

Answer 5

这就是我实现这样一个人的方式class，并附上一些评论。

//sort a person object by age first, then by last name
    class Person : IComparable<Person>, IComparable
    {
        public string LastName { get; }
        public string FirstName { get; }
        public int Age { get; }

        public Person(string vorname, string nachname, int age)
        {
            LastName = vorname;
            FirstName = nachname;
            Age = age;
        }

        // used by the default comparer
        public int CompareTo(Person p)
        {
            // make sure comparable being consistent with equality; this will use IEquatable<Person> if implemented on Person hence better than static Equals from object
            if (EqualityComparer<Person>.Default.Equals(this, p)) return 0;

            if (p == null)
                throw new ArgumentNullException(nameof(p), "Cannot compare person with null");

            if (Age.CompareTo(p.Age) == 0)
            {
                return LastName.CompareTo(p.LastName);
            }
            return Age.CompareTo(p.Age);
        }

        // explicit implementation for backward compatiability 
        int IComparable.CompareTo(object obj)
        {
            Person p = obj as Person;
            return CompareTo(p);
        }

        public override string ToString() => $"{LastName} {FirstName} \t {Age}";
    }

使用 first/last 名称和年龄 C# 对名称列表进行排序

Sorting a list of names with first/last name and age C#

c#

sorting

icomparable