C# |数组列表类

原文:https://www.geeksforgeeks.org/c-sharp-arraylist-class/

数组列表表示可以单独索引的对象的有序集合。它基本上是数组的替代。它还允许动态内存分配、添加、搜索和排序列表中的项目。

数组列表类的属性:

可以随时在数组列表集合中添加或删除元素。
数组列表不能保证排序。
数组列表的容量是数组列表可以容纳的元素数量。
可以使用整数索引访问此集合中的元素。此集合中的索引从零开始。
它还允许重复元素。
不支持在数组列表集合中使用多维数组作为元素。

构造器

示例:

// C# code to create an ArrayList
using System;
using System.Collections;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating an ArrayList
        ArrayList myList = new ArrayList();

        // Adding elements to ArrayList
        myList.Add("Hello");
        myList.Add("World");

        Console.WriteLine("Count : " + myList.Count);
        Console.WriteLine("Capacity : " + myList.Capacity);
    }
}

输出:

Count : 2
Capacity : 4

性能

示例:

// C# program to illustrate the 
// ArrayList Class Properties
using System; 
using System.Collections; 
using System.Collections.Generic; 

class GFG { 

    // Driver code 
    public static void Main() 
    { 

        // Creating an ArrayList 
        ArrayList myList = new ArrayList(); 

        // Adding elements to ArrayList 
        myList.Add("A"); 
        myList.Add("B"); 
        myList.Add("C"); 
        myList.Add("D"); 
        myList.Add("E"); 
        myList.Add("F"); 

        // -------- IsFixedSize Property --------

        // To check if the ArrayList has fixed size or not 
        Console.WriteLine(myList.IsFixedSize); 

        // -------- IsReadOnly Property --------

        // To check if the ArrayList is read-only or not 
        Console.WriteLine(myList.IsReadOnly); 
    } 
}

输出:

False
False

方法

例 1:

// C# code to check if an element is
// contained in ArrayList or not
using System;
using System.Collections;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating an ArrayList
        ArrayList myList = new ArrayList();

        // Adding elements to ArrayList
        myList.Add("A");
        myList.Add("B");
        myList.Add("C");
        myList.Add("D");
        myList.Add("E");
        myList.Add("F");
        myList.Add("G");
        myList.Add("H");

        // To check if the ArrayList Contains element "E"
        // If yes, then display it's index, else
        // display the message
        if (myList.Contains("E"))
            Console.WriteLine("Yes, exists at index " + myList.IndexOf("E"));
        else
            Console.WriteLine("No, doesn't exists");
    }
}

输出:

Yes, exists at index 4

例 2:

// C# code to remove a range of
// elements from the ArrayList
using System;
using System.Collections;
using System.Collections.Generic;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating an ArrayList
        ArrayList myList = new ArrayList(10);

        // Adding elements to ArrayList
        myList.Add(2);
        myList.Add(4);
        myList.Add(6);
        myList.Add(8);
        myList.Add(10);
        myList.Add(12);
        myList.Add(14);
        myList.Add(16);
        myList.Add(18);
        myList.Add(20);

        // Displaying the elements in ArrayList
        Console.WriteLine("The initial ArrayList: ");

        foreach(int i in myList)
        {
            Console.WriteLine(i);
        }

        // removing 4 elements starting from index 0
        myList.RemoveRange(0, 4);

        // Displaying the modified ArrayList
        Console.WriteLine("The ArrayList after Removing elements: ");

        // Displaying the elements in ArrayList
        foreach(int i in myList)
        {
            Console.WriteLine(i);
        }
    }
}

输出:

The initial ArrayList: 
2
4
6
8
10
12
14
16
18
20
The ArrayList after Removing elements: 
10
12
14
16
18
20

参考:

https://docs . Microsoft . com/en-us/dotnet/API/system . collections . ArrayList？视图=netframework-4.7.2

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