C# List.Select()

List.Select()：

　　①一般List中的元素是对象的时候，可以通过Selec()获取列表中所有元素的部分或者全部属性属性值列表；

　　②如果Select()中有判断的部分，则最终返回的列表是bool布尔类型的列表。

 

using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;

public class Test : MonoBehaviour
{
    /// <summary>
    /// 所有学生
    /// </summary>
    public List<Student> students = new List<Student>();

    private void Start()
    {
        //提取所有学生的姓名和性别
        foreach (var nameAndGender in ExtractAllStudentNameAndAge())
        {
            Debug.Log(nameAndGender.name +"，" + nameAndGender.gender);
        }

        //提取所有学生的学号
        foreach (var id in ExtractAllStudentId())
        {
            Debug.Log(id);
        }

        //每个学生年龄是否大于23
        foreach (var item in AgeOver23())
        {
            Debug.Log(item);
        }
    }

    #region 提取所有学生的姓名和性别

    /*//写法1
    List<dynamic> ExtractAllStudentNameAndAge()
    {
        List<dynamic> allId = students.Select(
               t => (dynamic)new { t.name, t.gender }
               ).ToList();

        return allId;
    }*/

    //写法2
    List<NameAndGender> ExtractAllStudentNameAndAge()
    {
        List<NameAndGender> allId = students.Select(
               t => new NameAndGender(t.name, t.gender)
               ).ToList();

        return allId;
    }
    #endregion

    #region 提取所有学生的学号

    /*//写法1
    List<dynamic> ExtractAllStudentId()
    {
        List<dynamic> allId = students.Select(
                t => (dynamic)t.id
                ).ToList();

        return allId;
    }*/

    //写法2
    List<int> ExtractAllStudentId()
    {
        List<int> allId = students.Select(
               t => (int)t.id
               ).ToList();

        return allId;
    }
    #endregion

    #region 每个学生年龄是否大于23

    /*//写法1
    List<dynamic> AgeOver23()
    {
        List<dynamic> allResult = students.Select(
               t => (dynamic)t.age > 23
               ).ToList();

        return allResult;
    }*/

    //写法2
    List<bool> AgeOver23()
    {
        List<bool> allResult = students.Select(
               t => t.age > 23
               ).ToList();

        return allResult;
    }
    #endregion
}
/// <summary>
/// 学生信息
/// </summary>
[System.Serializable]
public class Student
{
    /// <summary>
    /// 名字
    /// </summary>
    public string name;
    /// <summary>
    /// 年龄
    /// </summary>
    public int age;
    /// <summary>
    /// 学号
    /// </summary>
    public int id;
    /// <summary>
    /// 性别
    /// </summary>
    public Gender gender;

    public override string ToString()
    {
        return string.Format("{0}，{1}，{2}，{3}", name, age, id, gender == Gender.Female ? "女" : "男");
    }
}
/// <summary>
/// 性别
/// </summary>
public enum Gender
{
    /// <summary>
    /// 女性
    /// </summary>
    Female,
    /// <summary>
    /// 男性
    /// </summary>
    Male,
}
public class NameAndGender
{
    /// <summary>
    /// 名字
    /// </summary>
    public string name;
    /// <summary>
    /// 性别
    /// </summary>
    public Gender gender;
    public NameAndGender(string name, Gender gender)
    {
        this.name = name;
        this.gender = gender;
    }
    public override string ToString()
    {
        return string.Format("{0}，{1}", name, gender == Gender.Female ? "女" : "男");
    }
}