2.C#编程指南-数组

简介

数组是一种数据结构，它包含若干相同类型的变量。数组是使用类型声明的：

type[] arrayName;

1.数组可以是一维、多维或交错的。

//一维数组
int[] array = {1,2,3}
//多维数组
int[,] array = {{1,2},{3,4},{5,6}};
//交错数组：元素为数组的数组，因此其元素是引用类型并初始化为null。
int[][] jaggedArray = new int[3][];
jaggedArray[0] = new int[5];
jaggedArray[1] = new int[4];
jaggedArray[2] = new int[3];

2.数值数组元素的默认值设置为0，而引用元素的默认值设置为null。

3.交错数组是数组的数组，因此其元素是引用类型并初始为null。

4.数组的索引从0开始：具有n个元素的数组的索引从0到n-1。

5.数组元素可以是任何类型，包括数组类型。

6.数组类型是从抽象基类型Array派生的引用类型。由于此类型实现了IEnumberable和IEnumberable(Of T)，因些可以对C#中的所有数组使用foreach迭代。

 

作为对象的数组

在C#中，数组实际上是对象。Array是所有数组类型的抽象基类型。可以使用Array具有的属性以及其他类成员。

这种用法的一个示例是使用Length属性来获取数组的长度。

int[] numbers = {1,2,3,4,5};
int lengthOfNumbers = numbers.Length;

Array类提供了许多其他有用的方法和属性，用于排序、搜索和复制数组。

 

将数组作为参数传递(ChangeArray??)

class ArrayClass
{
    static void PrintArray(string[] arr)
    {
        for (int i = 0; i < arr.Length; i++)
        {
            System.Console.Write(arr[i] + "{0}", i < arr.Length - 1 ? " " : "");
        }
        System.Console.WriteLine();
    }

    static void ChangeArray(string[] arr)
    {
        // The following attempt to reverse the array does not persist when
        // the method returns, because arr is a value parameter.
        arr = (arr.Reverse()).ToArray();
        // The following statement displays Sat as the first element in the array.
        System.Console.WriteLine("arr[0] is {0} in ChangeArray.", arr[0]);
    }

    static void ChangeArrayElements(string[] arr)
    {
        // The following assignments change the value of individual array 
        // elements. 
        arr[0] = "Sat";
        arr[1] = "Fri";
        arr[2] = "Thu";
        // The following statement again displays Sat as the first element
        // in the array arr, inside the called method.
        System.Console.WriteLine("arr[0] is {0} in ChangeArrayElements.", arr[0]);
    }

    static void Main()
    {
        // Declare and initialize an array.
        string[] weekDays = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };

        // Pass the array as an argument to PrintArray.
        PrintArray(weekDays);

        // ChangeArray tries to change the array by assigning something new
        // to the array in the method. 
        ChangeArray(weekDays);

        // Print the array again, to verify that it has not been changed.
        System.Console.WriteLine("Array weekDays after the call to ChangeArray:");
        PrintArray(weekDays);
        System.Console.WriteLine();

        // ChangeArrayElements assigns new values to individual array
        // elements.
        ChangeArrayElements(weekDays);

        // The changes to individual elements persist after the method returns.
        // Print the array, to verify that it has been changed.
        System.Console.WriteLine("Array weekDays after the call to ChangeArrayElements:");
        PrintArray(weekDays);
    }
}
// Output: 
// Sun Mon Tue Wed Thu Fri Sat
// arr[0] is Sat in ChangeArray.
// Array weekDays after the call to ChangeArray:
// Sun Mon Tue Wed Thu Fri Sat
// 
// arr[0] is Sat in ChangeArrayElements.
// Array weekDays after the call to ChangeArrayElements:
// Sat Fri Thu Wed Thu Fri Sat