Week 5

1. C#Programming Arrays in C#Declaring Arrays of Different TypesInitializing ArrayAccessing Array ElementsCreating User Interfaces Using Windows Standards Form Application Types and StandardsLooking at Forms Week 5

2. ARRAYS • The array is the most common data structure, found in all programming languages. • Using an array in C# involves creating an array object of System.Arraytype, the abstract base type for all arrays. • The Array class provides a set of methods for performing tasks such as sorting and searching that programmers had to build by hand in the past.

3. Arrays • An interesting alternative to using arrays in C# is the ArrayList class. An arrayListis an array that grows dynamically as more space is needed. For situations where you can’t accurately determine the ultimate size of an array, or where the size of the array will change quite a bit over the lifetime of a program, an arrayListmay be a better choice than an array.

4. Arrays • Arrays are indexed collections of data. The data can be of either a built-in type or a user-defined type. • In fact, it is probably the simplest just to say that array data are objects. • Arrays in C# are actually objects themselves because they derive from the System.Arrayclass. • An array is a declared instance of the System.Array class, so we can use of all the methods and properties of this class when using arrays • In C#, arrays can be declared as fixed length or dynamic.

5. Declaring and Initializing Arrays • Arrays are declared using the following syntax: • type[] array-name; • where type is the data type of the array elements. Here is an example: • int[ ] intArray; • intArray = new int[5];

6. Defining arrays of different types • In C#, arrays are objects. That means that declaring an array doesn't create an array. After declaring an array, you need to instantiate an array by using the "new" operator. • The following syntax defines arrays of different data types double[] doubleArray = new double[5]; char[] charArray = new char[5]; bool[] boolArray = new bool[2]; string[] stringArray = new string[10];

7. Initializing Arrays • Once an array is declared, the next step is to initialize an array. The initialization process of an array includes adding actual data to the array. • The following sample syntaxes creates an array of 3 items and values of these items are added when the array is initialized. • int[] sArray= new int[3] {1, 3, 5}; • Alternative, we can also add array items one at a time as listed in the following code snippet. • int[ ] sArray= new int[3]; • sArray[0] = 1; • sArray[1] = 3; • sArray[2] = 5;

8. Initializing Arrays The following code declares a static type of array with integer values. • int[ ] x=new int[ ] {1,3,4,5,6}; • Console.WriteLine(x[3]); • Console.ReadLine(); The following code declares a dynamic array with string values. • string[ ] strArray = new string[] { “kamal", “Ali", “Raheel", "Praveen", “Mujeeb" };

9. Accessing Arrays • We can access an array item by passing the item index in the array. • The following syntax creates an array of three items and displays those items on the console. • int[] staticIntArray = new int[3]; • staticIntArray[0] = 1; • staticIntArray[1] = 3; • staticIntArray[2] = 5; • Console.WriteLine(staticIntArray[0]); • Console.WriteLine(staticIntArray[1]); • Console.WriteLine(staticIntArray[2]);

10. Accessing an array using a foreach Loop • The foreach control statement is used to iterate through the items of an array. • For example, the following code uses foreach loop to read all items of an array of strings. • string[ ] strArray = new string[] { “kamal", “Ali", “Raheel", "Praveen", “Mujeeb" }; • foreach(string str in strArray) { Console.WriteLine(str); } • The following code will access the elements of integer type array • foreach (int x in myArray) { Console.WriteLine(x); }

11. Setting and Accessing Array Elements • Elements are stored in an array either by direct access or by calling the Array class method SetValue. Direct access involves referencing an array position by index on the left-hand side of an assignment statement: • Names[2] = "Raymond"; • Sales[19] = 23123; • The SetValue method provides a more object-oriented way to set the value of an array element. The method takes two arguments, an index number and the value of the element. • names.SetValue["Raymond“,2]; • sales.SetValue[23123,5];

12. Setting and Accessing Array Elements • Array elements are accessed either by direct access or by calling the GetValuemethod. The GetValue method takes a single argument—an index. • myName = names[2]; • monthSales = sales.GetValue[19]; • Console.WriteLine(sales.GetValue[2]); • It is common to loop through an array in order to access every array element using a For loop. • A frequent mistake programmers make when coding the loop is to either hard-code the upper value of the loop call a function that accesses the upper bound of the loop for each iteration of the loop: • (for int i = 0; i <= sales.GetUpperBound(0); i++) • totalSales = totalSales + sales[i];

13. Methods and Properties for Retrieving Array Metadata • The Array class provides several properties for retrieving metadata about an array • Length: Returns the total number of elements in all dimensions of an array. • GetLength: Returns the number of elements in specified dimension of an array • Rank: Returns the number of dimensions of an array • GetType: Returns the Type of the current array instance

14. Assignment 2 • Write a program in which all the following functions using two different data types of arrays. • i.e. length, rank, getlength, get type

15. Array Types • Arrays can be divided into the following four categories. • Single-dimensional arrays • Multidimensional arrays or rectangular arrays • Jagged arrays • Mixed arrays.

16. Single Dimension Arrays • Single-dimensional arrays are the simplest form of arrays. These types of arrays are used to store number of items of a predefined type. All items in a single dimension array are stored contiguously starting from 0 to the size of the array -1. • The following code declares an integer array that can store 3 items. • int[] intArray; • intArray = new int[3];

17. Multi-Dimensional Arrays • A multi-dimensional array, also known as a rectangular array is an array with more than one dimension. The form of a multi-dimensional array is a matrix. • Syntax • int[ , ] xarray=new int[row,col]; Declaring a multi-dimensional array • A multi dimension array is declared as following: • string[,] mutliDimStringArray; • A multi-dimensional array can be fixed-sized or dynamic sized.

18. Initializing multi-dimensional arrays • The following code is an example of fixed-sized multi-dimensional arrays that defines two multi dimension arrays with a matrix of 3x2 and 2x2. • The first array can store 6 items and second array can store 4 items. Both of these arrays are initialized during the declaration. • int[,] numbers = new int[3, 2] { { 1, 2 }, { 3, 4 }, { 5, 6 } }; • string[,] names = new string[2, 2] { { “Isb", “Lhr” }, { “DHA", “Gulbarg" } };

19. Accessing multi-dimensional arrays • A multi-dimensional array items are represented in a matrix format and to access it's items, we need to specify the matrix dimension. • The following code shows how to access numbers array defined in the above code. • Console.WriteLine(numbers[0,0]); • Console.WriteLine(numbers[0, 1]); • Console.WriteLine(numbers[1, 0]); • Console.WriteLine(numbers[1, 1]); • Console.WriteLine(numbers[2, 0]); • Console.WriteLine(numbers[2, 2])

20. Parameter Arrays • A parameter array is specified in the parameter list of a method definition by using the keyword ParamArray. • The following method definition allows any amount of numbers to be supplied as parameters, with the total of the numbers returned from the method • static intsumNums(paramsint[] nums) { intsum = 0; for(inti = 0; i <= nums.GetUpperBound(0); i++) sum += nums[i]; return sum; }

21. Jagged Arrays • Data comes in various shapes. Sometimes the shape is uneven. • The C# language provides jagged arrays, which can store efficiently many rows of varying lengths. • Any type of data, reference or value, can be used.

22. Initializing Jagged Arrays • Jagged array can be used, its items must be initialized. • The following code initializes a jagged array; • intJaggedArray[0] = new int[2]; • intJaggedArray[1] = new int[4]; • intJaggedArray[2] = new int[6]; • We can also initialize a jagged array's items by providing the values of the array's items. • The following code initializes item an array's items directly during the declaration. • intJaggedArray[0] = new int[2]{2, 12}; • intJaggedArray[1] = new int[4]{4, 14, 24, 34}; • intJaggedArray[2] = new int[6] {6, 16, 26, 36, 46, 56 };

23. Accessing Jagged Arrays • We can access jagged array using loop through all of the items of a jagged array. • The Length property of an array helps a lot; it gives us the number of items in an array. • The following code loops through all of the items of a jagged array and displays them on the screen. for (int i = 0; i < intJaggedArray3.Length; i++) { System.Console.Write("Element({0}): ", i); for (int j = 0; j < intJaggedArray3[i].Length; j++) { System.Console.Write("{0}{1}", intJaggedArray3[i][j], j == (intJaggedArray3[i].Length - 1) ? "" : " "); } System.Console.WriteLine(); }

24. Accessing Jagged Arrays using System; class Program { static void Main() { int[ ][ ] jagged = new int[3][ ]; jagged[0] = new int[2]; jagged[0][0] = 1; jagged[0][1] = 2; jagged[1] = new int[1]; jagged[2] = new int[3] { 3, 4, 5 }; for (int i = 0; i < jagged.Length; i++) { int[] innerArray = jagged[i]; for (int a = 0; a < innerArray.Length; a++) { Console.Write(innerArray[a] + " "); } Console.WriteLine(); } Console.ReadLine(); } Output "1 2" "0" "3 4 5"

25. Mixed Arrays • Mixed arrays are a combination of multi-dimension arrays and jagged arrays. The mixed arrays type is removed from .NET 4.0.