List<T>泛型类

List<T>示例

这篇文章中，我们会用示例讨论List<T>泛型类；List<T>是目前隶属于System.Collections.Generic名称空间的集合类。List集合类是使用范围最广的泛型集合类之一。List<T>集合类是可以用索引进行处理一种强对象列表类型。List<T>提供了很多函数，用于搜索、排列和操作列表项。

通过使用List<T>我们可以创建任何类型的集合，比如，如果我们需要，我们可以创建string列表，整数列表，甚至也可以创建用户自定义的复杂类型的列表，如customers列表，products列表等等。我们需要记住的最重要的一点是当我们向集合中添加项目时，列表集合的容量会自动扩展。

List列表集合中的方法和属性

下面是列表集合中一些有用的方法和属性

1、Add(T value) :此函数是用于向列表集合的尾部添加类目；

2、Remove(T value)：此函数用于从 List<T> 中移除特定对象的第一个匹配项。。

3、RemoveAt(int index)：此函数用于查找元素的索引位置，然后从列表集合中进行移除。

4、Insert（int index ,T value）：此函数用于在指定索引位置插入元素。

5、Capacity：此属性用于返回存入列表集合中的能够容纳的元素数量。

List<T>实例

让我们用一个例子来了解一下上面提到的列表集合的函数和属性。所以，基本上，我们创建了一个整数类型的列表，然后用Add方法添加类目到集合中，下面的示例中有文字说明，所以请仔细查看。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace List
{
    class Program
    {
        static void Main(string[] args)
        {
            List<int> integerList = new List<int>();
            Console.WriteLine("初始时的容量：" + integerList.Capacity);

            integerList.Add(10);
            Console.WriteLine("加入第一个类目后的容量：" + integerList.Capacity);
            integerList.Add(20);
            integerList.Add(30);
            integerList.Add(40);
            Console.WriteLine("加入第4个类目后的容量：" + integerList.Capacity);
            integerList.Add(50);
            Console.WriteLine("加入第5个元素后的容量：" + integerList.Capacity);

            //用for循环打印
            Console.WriteLine("用for循环打印列表");
            for (int i = 0; i < integerList.Count; i++)
            {
                Console.WriteLine(integerList[i] + "  ");
            }
            Console.WriteLine();

            //自列表中移除类目
            integerList.Remove(30);
            Console.WriteLine("移除值30后的列表");
            foreach (int item in integerList)
            {
                Console.WriteLine(item + "  ");
            }
            Console.WriteLine();

            //在列表中加入数值
            integerList.Insert(2,25);
            Console.WriteLine("在列表的索引位置2中加入数值25");
            foreach (int item in integerList)
            {
                Console.WriteLine(item + "  ");
            }
            Console.WriteLine();

            List<int> newIntegerList = new List<int>(integerList);
            Console.WriteLine("新列表的初始容量：" + newIntegerList.Capacity);

            Console.WriteLine("打印由旧的列表创建的新列表");
            foreach (int item in newIntegerList)
            {
                Console.WriteLine(item + "  ");
            }
            Console.WriteLine();

            List<int> TheCapacity = new List<int>(10);
            Console.WriteLine("指定的List列表容量是：" + TheCapacity.Capacity);
            Console.ReadKey();
        }
    }
}

 复杂类型的列表集合

让我们看一个复杂类型的列表集合。下列代码中，创建一个Employee类，然后创建一些employee对象，再创建一个Employee类型的集合，将所有employee对象存储进集合中。最后，用List<T>泛型集合类提供的函数方法进行不同类型的操作。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ListCollection
{
    class Program
    {
        static void Main(string[] args)
        {
            Employee emp1 = new Employee()
            {
                ID = 101,
                Name = "Pranaya",
                Gender = "Male",
                Salary = 5000
            };
            Employee emp2 = new Employee
            {
                ID = 102,
                Name = "Priyanka",
                Gender = "Female",
                Salary = 7000
            };
            Employee emp3 = new Employee()
            {
                ID = 103,
                Name = "Anurag",
                Gender = "Male",
                Salary = 5500
            };
            Employee emp4 = new Employee()
            {
                ID = 104,
                Name = "Sambit",
                Gender = "Male",
                Salary = 6500
            };
            List<Employee> listEmployees = new List<Employee>();
            listEmployees.Add(emp1);
            listEmployees.Add(emp2);
            listEmployees.Add(emp3);

            Employee emp = listEmployees[0];
            Console.WriteLine("Retrive the First employee by index.");
            Console.WriteLine( "ID = {0},Name = {1},Gender = {2},Salary = {3}",emp.ID,emp.Name,emp.Gender,emp.Salary);
            Console.WriteLine();
        }
    }

    public class Employee
    { 
        public int ID { get; set; }
        public string Name { get; set; }
        public string Gender { get; set; }
        public int Salary { get; set; }
    }
}

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ListCollection
{
    class Program
    {
        static void Main(string[] args)
        {
            Employee emp1 = new Employee()
            {
                ID = 101,
                Name = "Pranaya",
                Gender = "Male",
                Salary = 5000
            };
            Employee emp2 = new Employee
            {
                ID = 102,
                Name = "Priyanka",
                Gender = "Female",
                Salary = 7000
            };
            Employee emp3 = new Employee()
            {
                ID = 103,
                Name = "Anurag",
                Gender = "Male",
                Salary = 5500
            };
            Employee emp4 = new Employee()
            {
                ID = 104,
                Name = "Sambit",
                Gender = "Male",
                Salary = 6500
            };
            List<Employee> listEmployees = new List<Employee>();
            listEmployees.Add(emp1);
            listEmployees.Add(emp2);
            listEmployees.Add(emp3);

            Employee emp = listEmployees[0];
            Console.WriteLine("Retrive the First employee by index.");
            Console.WriteLine( "ID = {0},Name = {1},Gender = {2},Salary = {3}",emp.ID,emp.Name,emp.Gender,emp.Salary);
            Console.WriteLine();

            Console.WriteLine("Retriving the first using for loop");
            for (int i = 0; i < listEmployees.Count; i++)
            {
                Employee employee = listEmployees[i];
                Console.WriteLine("ID = {0},Name = {1} , Gender = {2}, Salary = {3}",employee.ID,employee.Name,employee.Gender,employee.Salary);
            }
            Console.WriteLine();

            Console.WriteLine("Retriving the list using foreach loop");
            foreach (Employee e in listEmployees)
            {
                Console.WriteLine("ID = {0}, Name = {1}, Gender = {2}, Salary = {3}",
                                e.ID,e.Name,e.Gender,e.Salary);
            }
            Console.WriteLine();

            //在位置1插入一个Employee
            listEmployees.Insert(1,emp4);
            Console.WriteLine("Retriving the list after inserting new employee in index 1");
            foreach (Employee e   in listEmployees)
            {
                Console.WriteLine("ID = {0}, Name = {1}, Gender = {2}, Salary = {3}",
                                e.ID,e.Name,e.Gender,e.Salary);
            }
            Console.WriteLine();

            Console.WriteLine("Index of emp3 object in the list = " +
                                listEmployees.IndexOf(emp3));
            Console.ReadKey();
        }
    }

    public class Employee
    { 
        public int ID { get; set; }
        public string Name { get; set; }
        public string Gender { get; set; }
        public int Salary { get; set; }
    }
}

 

 注：所有 的泛型类在C#中都是强类型。那意味着如果我们创建 了Employee类型列表集合，那我们只能添加Employee类型的对象到列表中。如果我们尝试添加一个不同类型的对象，编译器会报错。