C# |获取或设置数组列表中指定索引处的元素

原文:https://www . geesforgeks . org/c-sharp-get-or-set-the-element-at-specific-index-in-ArrayList/

数组列表。项目[Int32]属性用于获取或设置 数组列表 中指定索引处的元素。

语法:

public virtual object this[int index] { get; set; }

这里,索引是要获取或设置的元素的从零开始的索引。

返回值:返回指定索引处的对象类型元素。

异常:如果指数小于零或等于或大于 计数 ,该属性将抛出argumentout of range 异常

以下程序说明了上述属性的使用:

例 1:

// C# code to get or set the element at
// the specified index in ArrayList
using System;
using System.Collections;

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");

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

        Console.WriteLine("After Item[int32] Property: ");

        // setting the value at index 2
        myList[2] = "Z";

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

Output:

A
B
C
D
E
F
After Item[int32] Property: 
A
B
Z
D
E
F

例 2:

// C# code to get or set the element at
// the specified index in 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
        // 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 the ArrayList
        foreach(int i in myList)
        {
            Console.WriteLine(i);
        }

        Console.WriteLine("After Item[int32] Property: ");

        // setting the value at index 8
        // this will give error as index
        // is greater than count
        myList[10] = 56;

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

运行时错误:

未处理异常: 系统。ArgumentOutOfRangeException:索引超出范围。必须是非负的,并且小于集合的大小。 参数名称:索引

参考: