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C#编程（5_数组）
数组具有以下属性：
数组可以是一维、多维或交错的。
当创建了数组实例时，将建立维度数和每个维度的长度。 在实例的生存期内，这些值不能更改。
数值数组元素的默认值设置为零，而引用元素的默认值设置为 null。
交错数组是数组的数组，因此其元素是引用类型并初始化为 null。
数组的索引从零开始：具有 n 个元素的数组的索引是从 0 到 n-1。
数组元素可以是任何类型，包括数组类型。
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 IEnumerable 和 IEnumerable<T>，因此可以对 C# 中的所有数组使用foreach 迭代。
下面的示例创建一维、多维和交错数组：
class TestArraysClass{ static void Main() { // Declare a single-dimensional array int[] array1 = new int[5]; // Declare and set array element values int[] array2 = new int[] { 1, 3, 5, 7, 9 }; // Alternative syntax int[] array3 = { 1, 2, 3, 4, 5, 6 }; // Declare a two dimensional array int[,] multiDimensionalArray1 = new int[2, 3]; // Declare and set array element values int[,] multiDimensionalArray2 = { { 1, 2, 3 }, { 4, 5, 6 } }; // Declare a jagged array int[][] jaggedArray = new int[6][]; // Set the values of the first array in the jagged array structure jaggedArray[0] = new int[4] { 1, 2, 3, 4 }; }}
多维数组：
// Two-dimensional array.int[,] array2D = new int[,] { { 1, 2 }, { 3, 4 }, { 5, 6 }, { 7, 8 } };// The same array with dimensions specified.int[,] array2Da = new int[4, 2] { { 1, 2 }, { 3, 4 }, { 5, 6 }, { 7, 8 } };// A similar array with string elements.string[,] array2Db = new string[3, 2] { { "one", "two" }, { "three", "four" }, { "five", "six" } };// Three-dimensional array.int[, ,] array3D = new int[,,] { { { 1, 2, 3 }, { 4, 5, 6 } }, { { 7, 8, 9 }, { 10, 11, 12 } } };// The same array with dimensions specified.int[, ,] array3Da = new int[2, 2, 3] { { { 1, 2, 3 }, { 4, 5, 6 } }, { { 7, 8, 9 }, { 10, 11, 12 } } };// Accessing array elements.System.Console.WriteLine(array2D[0, 0]);System.Console.WriteLine(array2D[0, 1]);System.Console.WriteLine(array2D[1, 0]);System.Console.WriteLine(array2D[1, 1]);System.Console.WriteLine(array2D[3, 0]);System.Console.WriteLine(array2Db[1, 0]);System.Console.WriteLine(array3Da[1, 0, 1]);System.Console.WriteLine(array3D[1, 1, 2]);// Getting the total count of elements or the length of a given dimension.var allLength = array3D.Length;var total = 1;for (int i = 0; i < array3D.Rank; i++) { total *= array3D.GetLength(i);}System.Console.WriteLine("{0} equals {1}", allLength, total);// Output:// 1// 2// 3// 4// 7// three// 8// 12// 12 equals 12
交错数组：
class Program{ static void Main(string[] args) { // Declare the array of two elements: int[][] arr = new int[2][]; // Initialize the elements: arr[0] = new int[5] { 1, 3, 5, 7, 9 }; arr[1] = new int[4] { 2, 4, 6, 8 }; // Display the array elements: for (int i = 0; i < arr.Length; i++) { System.Console.Write("Element({0}): ", i); for (int j = 0; j < arr[i].Length; j++) { System.Console.Write("{0}{1}", arr[i][j], j == (arr[i].Length - 1) ? "" : " "); } System.Console.WriteLine(); } // Keep the console window open in debug mode. System.Console.WriteLine("Press any key to exit."); System.Console.ReadKey(); Console.ReadKey(); /* Output: Element(0): 1 3 5 7 9 Element(1): 2 4 6 8*/ }};
对数组使用foreach：
int[] numbers = { 4, 5, 6, 1, 2, 3, -2, -1, 0 };foreach (int i in numbers){ System.Console.Write("{0} ", i);}// Output: 4 5 6 1 2 3 -2 -1 0
int[,] numbers2D = new int[3, 2] { { 9, 99 }, { 3, 33 }, { 5, 55 } };// Or use the short form:// int[,] numbers2D = { { 9, 99 }, { 3, 33 }, { 5, 55 } };foreach (int i in numbers2D){ System.Console.Write("{0} ", i);}// Output: 9 99 3 33 5 55
将数组作为参数传递：
在下面的示例中，将初始化一个字符串数组并将其作为参数传递到字符串的 PrintArray 方法。 该方法显示数组的元素。 接下来，调用 ChangeArray和 ChangeArrayElement 方法以演示通过值发送数组参数时不会阻止更改这些数组元素。
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); Console.ReadKey(); }}// 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
class ArrayClass2D{ static void Print2DArray(int[,] arr) { // Display the array elements. for (int i = 0; i < arr.GetLength(0); i++) { for (int j = 0; j < arr.GetLength(1); j++) { System.Console.WriteLine("Element({0},{1})={2}", i, j, arr[i, j]); } } } static void Main() { // Pass the array as an argument. Print2DArray(new int[,] { { 1, 2 }, { 3, 4 }, { 5, 6 }, { 7, 8 } }); // Keep the console window open in debug mode. System.Console.WriteLine("Press any key to exit."); System.Console.ReadKey(); }}/* Output: Element(0,0)=1 Element(0,1)=2 Element(1,0)=3 Element(1,1)=4 Element(2,0)=5 Element(2,1)=6 Element(3,0)=7 Element(3,1)=8*/
在此示例中，在调用方（Main 方法）中声明数组 theArray，并在 FillArray 方法中初始化此数组。 然后，数组元素将返回调用方并显示。
class TestOut{ static void FillArray(out int[] arr) { // Initialize the array: arr = new int[5] { 1, 2, 3, 4, 5 }; } static void Main() { int[] theArray; // Initialization is not required // Pass the array to the callee using out: FillArray(out theArray); // Display the array elements: System.Console.WriteLine("Array elements are:"); for (int i = 0; i < theArray.Length; i++) { System.Console.Write(theArray[i] + " "); } // Keep the console window open in debug mode. System.Console.WriteLine("Press any key to exit."); System.Console.ReadKey(); }} /* Output: Array elements are: 1 2 3 4 5 */
在此示例中，在调用方（Main 方法）中初始化数组 theArray，并通过使用 ref 参数将其传递给 FillArray 方法。 在 FillArray 方法中更新某些数组元素。 然后，数组元素将返回调用方并显示。
class TestRef{ static void FillArray(ref int[] arr) { // Create the array on demand: if (arr == null) { arr = new int[10]; } // Fill the array: arr[0] = 1111; arr[4] = 5555; } static void Main() { // Initialize the array: int[] theArray = { 1, 2, 3, 4, 5 }; // Pass the array using ref: FillArray(ref theArray); // Display the updated array: System.Console.WriteLine("Array elements are:"); for (int i = 0; i < theArray.Length; i++) { System.Console.Write(theArray[i] + " "); } // Keep the console window open in debug mode. System.Console.WriteLine("Press any key to exit."); System.Console.ReadKey(); }} /* Output: Array elements are: 1111 2 3 4 5555 */
C#编程（5_数组）
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