ARRAYS in C#.NET

Maker DataMatrix in C#.NET ARRAYS

A jagged array is an array of arrays. Unlike rectangular arrays, the sub-arrays of a jagged array can have different numbers of elements. For example, the following code declares a two-dimensional jagged array. The array s layout in memory is shown in Figure 14-10. The length of the first dimension is 3. The declaration can be read as jagArr is an array of three arrays of ints. Notice that the figure shows four array objects one for the top-level array, and three for the sub-arrays. int[][] jagArr = new int[3][]; ... // Declare and create top-level array. // Declare and create sub-arrays.

The declaration syntax for jagged arrays requires a separate set of square brackets for each dimension. The number of sets of square brackets in the declaration of the array variable determines the rank of the array. A jagged array can be of any number of dimensions greater than one. As with rectangular arrays, dimension lengths cannot be included in the array type section of the declaration. Rank specifiers int[][] SomeArr; int[][][] OtherArr; Array type Array name

You can combine the jagged array declaration with the creation of the first-level array using an array creation expression, such as in the following declaration. The result is shown in Figure 14-11. Three sub-arrays int[][] jagArr = new int[3][];

Figure 14-11. Shortcut first-level instantiation You cannot instantiate more than the first-level array in the declaration statement. Allowed int[][] jagArr = new int[3][4]; Not allowed

Unlike other types of arrays, you cannot fully instantiate a jagged array in a single step. Since a jagged array is an array of independent arrays each array must be created separately. Instantiating a full jagged array requires the following steps: 1. First, instantiate the top-level array. 2. Next, instantiate each sub-array separately, assigning the reference to the newly created array to the appropriate element of its containing array. For example, the following code shows the declaration, instantiation, and initialization of a two-dimensional jagged array. Notice in the code that the reference to each sub-array is assigned to an element in the top-level array. The progression of steps 1 through 4 in the code correspond to the numbered representations in Figure 14-12. int[][] Arr = new int[3][]; Arr[0] = new int[] {10, 20, 30}; Arr[1] = new int[] {40, 50, 60, 70}; Arr[2] = new int[] {80, 90, 100, 110, 120}; // 1. Instantiate top level // 2. Instantiate sub-array // 3. Instantiate sub-array // 4. Instantiate sub-array

Since the sub-arrays in a jagged array are themselves arrays, it is possible to have rectangular arrays inside jagged arrays. For example, the following code creates a jagged array of three twodimensional rectangular arrays and initializes them with values. It then displays the values. The structure is illustrated in Figure 14-13. The code also uses the GetLength(int n) method of arrays, inherited from System.Array, to get the length of the specified dimension of the array. int[][,] Arr; // An array of 2-D arrays Arr = new int[3][,]; // Instantiate an array of three 2-D arrays. Arr[0] = new int[,] { { 10, 20 }, { 100, 200 } }; Arr[1] = new int[,] { { 30, 40, 50 }, { 300, 400, 500 } }; Arr[2] = new int[,] { { 60, 70, 80, 90 }, { 600, 700, 800, 900 } }; Get length of dimension 0 of Arr for (int i = 0; i < Arr.GetLength(0); i++) { Get length of dimension 0 of Arr[ i ] for (int j = 0; j < Arr[i].GetLength(0); j++) { Get length of dimension 1 of Arr[ i ] for (int k = 0; k < Arr[i].GetLength(1); k++) { Console.WriteLine ("[{0}][{1},{2}] = {3}", i, j, k, Arr[i][j, k]); } Console.WriteLine(""); } Console.WriteLine(""); }