1. Module 8 & 9 Method :Part I & Array :Part II
Thanawin Rakthanmanon
Create by: Aphirak Jansang
Computer Engineering Department
Kasetsart University, Bangkok THAILAND

2. Outlines
Array Review
Multi-dimensional Array Review
Method Overview

3. Array examples 1 2 3 4 5 score 1 2 3 score 5 6 7 9
review
Array examples
int [] score = new int[6]; 1 2 3 4 5
score
int [] score = new int[4] {5,6,7,9}; 1 2 3
score 5 6 7 9

4. Accessing Array Elements
review
Accessing Array Elements
Supply an integer index for accessing array elements
indexes are zero-based
int [] score = new int[4]; 1 2 3
score -3 7
score[0] = -3;
score[3] = 7;
Console.WriteLine(score[3]); 7

5. How to find Array’s length?
review
How to find Array’s length?
By property Length 4
int [] matrix = new int[4];
Console.WriteLine(matrix.Length);
By method GetLength() 7
int [] matrix = new int[7];
Console.WriteLine(matrix.GetLength(0));

6. foreach foreach = “for each element in an array” Syntax:
review
foreach
foreach = “for each element in an array”
Syntax:
foreach (var_declaration in array_name)
statement
// the above statement will be applied to each element in an array

7. foreach example string s = Console.ReadLine(); int count = 0;
review
foreach example
string s = Console.ReadLine();
int count = 0;
for (int i = 0; i < s.Length; i++){
if(s[i] == 'A') count++; }
string s = Console.ReadLine();
int count = 0;
foreach (char c in s) {
if (c == 'A')
count++; }

8. Outlines
Array Review
Multi-dimensional Array
Method Overview

9. Multi-dimensional Array’s declaration
Syntax:
<type> [ , ] <name>;
<type> [ , , ] <name>;
Creation:
<name> = new <type>[<dim1>,<dim2>];
2 dimensions
3 dimensions
2 dimensions

10. Array Declaration Example
int [ , ] grid2;
grid2 = new int [3,2];
int [ , , ] grid3;
grid3 = new int [3, 2, 4];

11. More examples 4 3 5 2 1 grid[1,1] == ? grid[1,2] == ? grid[0,2] == ? 1 5 4 3 2 1
grid[1,1] == ?
grid[1,2] == ?
grid[0,2] == ?
grid.GetLength(0) == ?
grid.GetLength(1) == ?
grid.Length == ? 1 3
new int[2, 3] 2 3 6

12. How to find Array’s #dimension?
By property Rank
int [] matrix = new int[5];
Console.WriteLine(matrix.Rank); 1
int [,] matrix = new int[5,2];
Console.WriteLine(matrix.Rank); 2
int [,,] matrix = new int[5,2,3];
Console.WriteLine(matrix.Rank); 3

13. Outline Method Overview Using Method Parameter Passing in Method
Pass by value
Pass by reference

14. a function/procedure owned by class.
What is Method?
Method is
a function/procedure owned by class.
System.Console.WriteLine(“Hello Kitty!!!”);

15. Pre-defined Method in C#
Console.WriteLine(”Hello, Kitty”);
double j = Math.Sqrt(4);
int N = int.Parse(”7”);
Console.WriteLine(”{0} = {1} + {2}”, 5, 3, 2);

16. How to call method in C#? Non-Returned Value - Procedure
Console.WriteLine(“Hello, Kitty!!!”);
Returned Value – Function
J = Math.Max(5, 20);
Parameter
Method Name
Class Name
Parameter
Variable
Class Name
Method Name

17. Method Idea name age width high DispAge CalArea area
Return no value (void)
Return Value

18. Method Example 1 4 1 3 2

19. Outline Method Overview Using Method Parameter Passing in Method
Pass by value
Pass by reference

20. Using User-Defined Method
1.Define Method
2.Call Method

21. Define Method in C# #remark return-type can be
static <return-type> <method-name>(<parameter list>) {
<const/variable declaration>;
<statements>; }
#remark return-type can be
data type = int, double, string, …
need return statement
void = return no value

22. Method Declaration Example
static void displaybox() { }
static int calage() { }
static int calbox(int x,y;) { }

23. Example1: Non-Returned Value
using System;
class NReturned {
static void Main() {
Console.WriteLine(”Hello, Pattara”); }

24. Example1: Non-Returned Value
using System;
class NReturned {
static void HelloP() {
Console.WriteLine(”Hello, Pattara”); }
static void Main() {
HelloP();
Hello Pattara

25. Example2: Non-Returned Value with parameters
using System;
class NReturned {
static void Main() {
Console.WriteLine(”Hi, AAA”);
Console.WriteLine(”Hi, BBB”);
Console.WriteLine(”Hi, CCC”); }

26. Example2: Non-Returned Value with parameters
using System;
class NReturned {
static void Hi(string s) {
Console.WriteLine(”Hello, {0}”, s); }
static void Main() {
Hi(”AAA”);
Hi(”BBB”);
Hi(”CCC”);
Hello, AAA
Hello, BBB
Hello, CCC

27. Example3: Returned Value
using System;
class Returned {
static void Main() {
int j;
j = 2*2;
Console.WriteLine(”{0}”, j);
j = 5*5; }

28. Example3: Returned Value
using System;
class Returned {
static double Power2(int n) {
return n*n; }
static void Main() {
double j;
j = Power2(2); //j=2*2;
Console.WriteLine(”{0}”, j);
j = Power2(5); //j=5*5; 4 25

29. C# Structure – Multiple Methods
Namespace
Class
Main()
Method1()
Method2()
Method3()
Method_N()

30. Variable & Constant Location
C# Structure - Methods
Namespace
Class
Main()
Variable & Constant Location
statements
Method1()
Variable & Constant
statements
Method2()
Variable & Constant
statements

31. Self Test 1 Define Power4(n) Method Ex. int j = Power4(2); //Return 16
Return n*n*n*n
Ex. int j = Power4(2); //Return 16
static ____ Power4(___________________) { }

32. Self Test 2 Define Max(x, y) Method
Return Max Value
Ex. int j = Max(5, 20); //Return 20
static ____ MAX(___________________) { }

33. Outline Method Overview Using Method Parameter Passing in Method
Pass by value
Pass by reference

34. Passing Parameter Type
Passing Type
Pass by value
Pass by
reference

35. Method Example: with return value
*Methods can return only single value. …
int x = power3(2); …
static int power3(int n) {
int j = n * n * n; return j; }

36. Parameter Passing in C#
Parameter Passing Location
static <return-type> <method-name>(<parameter list>) {
<const/variable declaration>;
<statements>; }

37. Pass by value Example Copy value s to st static void Main(){ string s;
s = "SuperMan2";
DisplayMovie(s);
Console.WriteLine(s); }
s = "SuperMan2"
Copy value s to st
s = st ="SuperMan2"
static void DisplayMovie(string st) {
Console.WriteLine("Movie = {0}",st);
st = "SpiderMan"; }
Movie = SuperMan2
SuperMan2

38. Pass by reference Example
static void Main(){
string s;
s = "SuperMan2";
DisplayMovie(ref s);
Console.WriteLine(s); }
s = "SuperMan2"
s is referred by st
st = s ="SpiderMan"
st = s ="SuperMan2"
static void DisplayMovie(ref string st) {
Console.WriteLine("Movie = {0}",st);
st = "SpiderMan"; }
Movie = SuperMan2
Changes st / changes s too
SpiderMan

39. Summary Defining Method Calling Method Parameter Passing in Method
No-Returned Value
Returned Value
Parameter Passing in Method
Pass by value
Pass by reference