C# basic knowledge compilation: basic knowledge (14) array

No matter which language, there will definitely be the concept of collection. The simplest and most intuitive collection should be an array. An array is a continuous space in memory. Take a look at the definition of array

in C#.
1. int[] intArry;
intArry= new int[6];
Here declares an int array type variable intArry and saves an int array object with 6 units;
int [,] intArry2 = new int[3, 4];
Declare an int two-dimensional array type variable and initialize an array object with 3 rows and 4 columns;
int[][] intArry3 = new int[9 ][];
Declare an array unit as an array variable of int array type. Each array element is an object reference of int array type.
Because it is an object-oriented language, references and objects are mentioned above. In fact:
1. The .net Frameword array is not a simple data structure, but a type, called an array type;
2. The array variable in the .net Framework stores references to array type objects. That is to say, the array is an object.
All .net Framework arrays (int[], string[], object[]) are subclasses inherited from Array. Generally, the Array class is not used directly, because various languages ​​under the .net Framework, including C# of course, map array objects to their own special syntax, such as int[], string[].

The array mainly has two attributes: index and length, that is, index and length. The index is used to access the elements in the array object, and the length is the length of the array.

Look at a piece of contact code:

public class MyArray
    {
        /// <summary>
        /// 定义数组测试
        /// </summary>
        public void TestInt()
        {
            int[] intArry1 = null;

            intArry1 = new int[6];

            int[,] intArry2 = new int[3, 4];

            int[][] intArry3 = new int[9][];
        }
        
        /// <summary>
        /// 值类型数组转引用类型数组测试
        /// </summary>
        /// <param name="array"></param>
        /// <returns></returns>
        public static object[] Int32ToArrayOfObject(int[] array)
        {
            object[] objArray = new object[array.Length];

            for (int i = 0; i < array.Length; i++)
            {
                objArray[i] = array[i];
            }

            return objArray;
        }
        /// <summary>
        /// 数组的主要特性测试
        /// </summary>
        public static void MainTest()
        {
            //声明一个包含是个元素的字符串型数组
            string[] sArray = new string[10];
            //访问数组
            //赋值
            for (int i = 0; i < sArray.Length; i++)
            {
                sArray[i] = @"string" + i;
            }

            ConsoleToClientString(sArray);

            //另一种方式声明数组，所谓的枚举法
            sArray = new string[] { "TestString0", "TestString1", "TestString2" };

            ConsoleToClientString(sArray);

            //数组复制
            string[] newSArray = sArray.Clone() as string[];

            ConsoleToClientString(newSArray);

            //使用Array的CreateInstance方法声明10元素的整形数组
            int[] intArray = Array.CreateInstance(typeof(int), 10) as int[];

            for (int i = 0; i < intArray.Length; i++)
            {
                intArray[i] = i;
            }

            ConsoleToClientInt(intArray);

            //数组之间的复制，指定位置，指定长度
            int[] newIntArray = new int[20];

            Array.Copy(intArray, 3, newIntArray, 4, intArray.Length - 3);

            ConsoleToClientInt(newIntArray);

            object[] objArray = sArray;

            ConsoleToClientObject(objArray);

            objArray = Int32ToArrayOfObject(intArray);

            ConsoleToClientObject(objArray);

            //数组的数组
            int[][] intArrayArray = new int[9][];

            Console.WriteLine("数组长度：" + intArrayArray.Length);

            //赋值
            for (int i = 1; i < 10; i++)
            {
                intArrayArray[i - 1] = new int[i];

                for (int j = 1; j <= i; j++)
                {
                    intArrayArray[i - 1][j - 1] = i * j;
                }
            }

            ConsoleToClientArrayArrayInt(intArrayArray);
            
            //二维数组
            int[,] intArray2D = new int[9, 9];

            Console.WriteLine(string.Format("二维数组 长度：{0},维数：{1}*{2}", intArray2D.Length, 

intArray2D.GetLength(0), intArray2D.GetLength(1)));

            for (int i = 1; i < 10; i++)
            {
                for (int j = 1; j <= i; j++)
                {
                    intArray2D[i - 1, j - 1] = i * j;
                }
            }

            int count = 0;

            foreach (int item in intArray2D)
            {
                if (item > 0)
                {
                    Console.Write("{0,2}", item);
                }

                if (++count >= 9)
                {
                    Console.WriteLine();

                    count = 0;
                }
            }
        }

        static void ConsoleToClientArrayArrayInt(int[][] intArrayArray)
        {
            foreach (int[] item1 in intArrayArray)
            {
                foreach (int item2 in item1)
                {
                    Console.Write("{0,2}", item2);
                }

                Console.WriteLine();
            }

            Console.WriteLine();
        }

        static void ConsoleToClientString(string[] sArray)
        {
            foreach (string item in sArray)
            {
                Console.Write(item + @",");
            }

            Console.WriteLine();
        }

        static void ConsoleToClientInt(int[] intArray)
        {
            foreach (int item in intArray)
            {
                Console.Write(item + @",");
            }

            Console.WriteLine();
        }

        static void ConsoleToClientObject(object[] objArray)
        {
            foreach (object item in objArray)
            {
                Console.Write(item.ToString() + @",");
            }

            Console.WriteLine();
        }

    }

Call

    class Program
    {
        static void Main(string[] args)
        {
            MyArray.MainTest();

            Console.ReadLine();
        }
    }

Result

You can know from the above: The array has a reference Type array and value type array. For reference type array, the element is used to save the reference of the object, and the initialization value is null; for value type array, the element saves the value of the

object, and for the numeric type, the initialization value is 0.

Arrays have dimensions, but multidimensional arrays and arrays of arrays are different concepts. intArrayArray and intArray2D are different. The array of array represents an m*n determinant

, and the multidimensional array is an array in which each element is an array object.

Arrays, like other collection classes, implement the ICollection interface and have enumeration and iteration functions.

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