C#中从指定索引获取Collection 的元素
给定一个整数类型的Collection<T>和一个索引，我们必须从给定索引访问元素。
要访问Collection<T>的元素，我们使用Collection<T>.Item[Int32index]属性。
语法：
Collection<T>.Item[Int32 index];
注意：如果index小于0或大于count，则可能返回异常（ArgumentOutOfRangeException）。
用C＃代码访问Collection<T>的元素
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
class nhooo
{
public static void Main()
{
//声明整数的集合
Collection<int> iColl = new Collection<int>();
//向集合中添加元素
iColl.Add(100);
iColl.Add(200);
iColl.Add(300);
iColl.Add(400);
//显示元素总数
Console.WriteLine("Total number of elements: " + iColl.Count);
//显示给定索引中的元素
Console.WriteLine("Element at index " + 0 + " is: " + iColl[0]);
Console.WriteLine("Element at index " + 1 + " is: " + iColl[1]);
Console.WriteLine("Element at index " + 2 + " is: " + iColl[2]);
Console.WriteLine("Element at index " + 3 + " is: " + iColl[3]);
}
}输出结果
Total number of elements: 4 Element at index 0 is: 100 Element at index 1 is: 200 Element at index 2 is: 300 Element at index 3 is: 400
显示异常
在这里，我们将从-1索引访问一个元素，该元素将生成“ArgumentOutOfRangeException”异常。
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
class nhooo
{
public static void Main()
{
//声明整数的集合
Collection<int> iColl = new Collection<int>();
//向集合中添加元素
iColl.Add(100);
iColl.Add(200);
iColl.Add(300);
iColl.Add(400);
//显示元素总数
Console.WriteLine("Total number of elements: " + iColl.Count);
//显示给定索引中的元素
Console.WriteLine("Element at index " + 0 + " is: " + iColl[0]);
Console.WriteLine("Element at index " + 1 + " is: " + iColl[1]);
Console.WriteLine("Element at index " + 2 + " is: " + iColl[2]);
Console.WriteLine("Element at index " + 3 + " is: " + iColl[3]);
//显示来自索引“-1”的元素"-1"
Console.WriteLine("Element at index " + -1 + " is: " + iColl[-1]);
}
}输出结果
Total number of elements: 4 Element at index 0 is: 100 Element at index 1 is: 200 Element at index 2 is: 300 Element at index 3 is: 400 Unhandled Exception: System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index at System.ThrowHelper.ThrowArgumentOutOfRange_IndexException () [0x0000c] in <65984520577646ec9044386ec4a7b3dd>:0 at System.Collections.Generic.List`1[T].get_Item (System.Int32 index) [0x00009] in <65984520577646ec9044386ec4a7b3dd>:0 at System.Collections.ObjectModel.Collection`1[T].get_Item (System.Int32 index) [0x00000] in <65984520577646ec9044386ec4a7b3dd>:0 atnhooo.Main() [0x00129] in <775a4ba6f9ff4ee287095185056138d8>:0 [ERROR] FATAL UNHANDLED EXCEPTION: System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index at System.ThrowHelper.ThrowArgumentOutOfRange_IndexException () [0x0000c] in <65984520577646ec9044386ec4a7b3dd>:0 at System.Collections.Generic.List`1[T].get_Item (System.Int32 index) [0x00009] in <65984520577646ec9044386ec4a7b3dd>:0 at System.Collections.ObjectModel.Collection`1[T].get_Item (System.Int32 index) [0x00000] in <65984520577646ec9044386ec4a7b3dd>:0 atnhooo.Main() [0x00129] in <775a4ba6f9ff4ee287095185056138d8>:0