C# custom type arrays and Array class

Array of custom type

using System;    
namespace ConsoleApplication4    
{    
    class Program    
    {    
        static void Main(string[] args)    
        {    
            Person[] myPersons = new Person[2];    
            myPersons[0] = new Person("Lilian", "Chen");    
            myPersons[1] = new Person("1", "2");    
            Console.WriteLine(myPersons[0].ToString());    
            Console.WriteLine(myPersons[1].ToString());    
            // 对自定义类型使用数组初始化器    
            Person[] persons = new Person[] {new Person("a", "b"), new Person("c", "d")};    
            Console.WriteLine(persons[1].ToString());    
            Console.ReadLine();    
        }    
    }    
    public class Person    
    {    
        public Person()    
        { }    
        public Person(string firstName, string lastName)    
        {    
            this.FirstName = firstName;    
            LastName = lastName;    
        }    
        public string FirstName    
        {    
            get;    
            set;    
        }    
        public string LastName    
        {    
            get;    
            set;    
        }    
        public override string ToString()    
        {    
            return String.Format("{0} {1}", FirstName, LastName);    
        }    
    }    
}

Note: If the elements in the array are reference types, memory must be allocated for each array element.

myPersons is a variable stored on the stack that references an array of Person elements stored on the managed heap. Each item in the array references a Person object.

Create an array

Declaring an array with [] is a notation for using the Array class in C#, and a new class derived from the abstract base class Array will be created behind the scenes. This allows you to use the methods and properties defined by the Array class for each C# array.

The Array class is an abstract class, so you cannot use the constructor to create an array. But in addition to creating an array instance using C# syntax, you can also create an array using the static method CreateInstance() (which can be used if the type of the element is not known in advance).

using System;    
namespace ConsoleApplication5    
{    
    class Program    
    {    
        static void Main(string[] args)    
        {    
            // CreateInstance 方法的第一个参数是元素的类型，第二个参数是数组的大小    
            Array intArray = Array.CreateInstance(typeof(int), 5);    
            for (int i = 0; i < intArray.Length; i++)    
            {    
                // 使用 SetValue() 方法设置值    
                intArray.SetValue(i, i);    
            }    
            for (int i = 0; i < intArray.Length; i++)    
            {    
                // 使用 GetValue() 方法读取值    
                Console.WriteLine(intArray.GetValue(i));    
                Console.ReadLine();    
            }    
            // 将已经创建的数组强制转换成声明为 int[] 的数组    
            int[] intArray1 = (int[])intArray;    
            Console.WriteLine(intArray1.Length);    
        }    
    }    
}

Use the CreateInstance() method to create multi-dimensional arrays and non-0-based arrays:

using System;    
namespace ConsoleApplication4    
{    
    class Program    
    {    
        static void Main(string[] args)    
        {    
            int[] lengths = { 2, 3 };    
            int[] lowerBounds = { 1, 10 };    
            Array racers = Array.CreateInstance(typeof(Person), lengths, lowerBounds);    
            racers.SetValue(new Person("a", "b"), 1, 10);    
            racers.SetValue(new Person("c", "d"), 1, 11);    
            racers.SetValue(new Person("e", "f"), 1, 12);    
            racers.SetValue(new Person("g", "h"), 2, 10);    
            racers.SetValue(new Person("i", "j"), 2, 11);    
            racers.SetValue(new Person("k", "l"), 2, 12);    
            Person[,] racers1 = (Person[,])racers;    
            Person first = racers1[1, 10];    
        }    
    }    
    public class Person    
    {    
        public Person()    
        { }    
        public Person(string firstName, string lastName)    
        {    
            this.FirstName = firstName;    
            LastName = lastName;    
        }    
        public string FirstName    
        {    
            get;    
            set;    
        }    
        public string LastName    
        {    
            get;    
            set;    
        }    
        public override string ToString()    
        {    
            return String.Format("{0} {1}", FirstName, LastName);    
        }    
    }    
}

Copy array

1) If the elements of the array are value types, all values ​​will be copied

int[] intArray1 = { 1, 2 };    
// 如果删掉 “（int[]）” 会有 Error “Cannot implicitly convert type ‘object’ to 'int[]'”    
int[] intArray2 = (int[]) intArray1.Clone

If the array contains If the reference type is a reference type, the element will not be copied, but only the reference will be copied. If you modify the attribute of an element in beatlesClone, the corresponding object in beatles will be changed.

Person[] beatles = { new Person("John", "Lennon"), new Person("Paul", "McCartney") };    
Person[] beatlesClone = (Person[])beatles.Clone();

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