05_Methods.pdf

Shoolini University Yogananda School of AI, Computing & Data Science C# Programming(CSU1531)   Methods Outline 9/12/2024 C# - Methods A method is a group of statements that together perform a task. Every C# program has at le...

Shoolini University Yogananda School of AI, Computing & Data Science C# Programming(CSU1531)   Methods Outline 9/12/2024 C# - Methods A method is a group of statements that together perform a task. Every C# program has at least one class with a method named Main. To use a method, you - Define the method need to − - Call the method Defining Methods in C#  When you define a method, you basically declare the elements of its structure.  The syntax for defining a method in C# is as follows − (Parameter List) { // Method Body } Cont.…  Following are the various elements of a method −  Access Specifier  This determines the visibility of a variable or a method from another class.  Return type  A method may return a value.  The return type is the data type of the value the method returns.  If the method is not returning any values, then the return type is void.  Method name  Method name is a unique identifier and it is case sensitive.  It cannot be same as any other identifier declared in the class.  Parameter list  Enclosed between parentheses, the parameters are used to pass and receive data from a method.  The parameter list refers to the type, order, and number of the parameters of a method.  Parameters are optional; that is, a method may contain no parameters.  Method body  This contains the set of instructions needed to complete the required activity. Example static void MyMethod() { Console.WriteLine("I just got executed!"); } static void Main(string[] args) { MyMethod(); } // Outputs "I just got executed!" Different Parts of a Method/Function  Example using System; static void Main(string[] args) { namespace CalculatorApplication { int a = 100; class MyClass { int b = 200; public int FindMax(int n1, int n2) int ret; { MyClass n = new MyClass(); int result; ret = n.FindMax(a, b); if (n1 > n2) Console.WriteLine("Max is : result = n1; {0}", ret ); else Console.ReadLine(); result = n2; } return result; } } } Types of Methods  Built-In Methods:  User-Defined Methods Which are already defined in the Defined by the developer or framework and available to be programmer explicitly. used by the developer or It reduces the complexity of a big programmer. program and optimizes the code Example: (Discussed in this ppt. so far)  WriteLIne function to print the output on the console window and  built-in Sqrt function to get the square root of a given number.  Parameters of a method  Here we are passing two values, x, and y, to the Add function, which takes two parameters (a and b).  The parameters (x and y) that we are passing to the Add function are called Actual Parameters.  The parameters (a and b) which are taken by the Add method are called Formal Parameters.  When we call the Add method, the values of actual parameters are copied to the formal parameters. So, the x value, i.e., 10, is copied to a, and the y value, i.e., 15, is copied to b. Types of User-Defined Functions in C#  Example: Methods with No using System; Argument and No namespace FunctionDemo { Return Type: class Program { static void Main(string[] args) When a method has no { arguments, it does not Sum(); receive any data from the Console.ReadKey(); calling method. Similarly, when it does not return a } value, the calling function static void Sum() does not receive any data { from the called method. int x = 10; int y = 20; int sum = x + y; Console.WriteLine($"Sum of {x} and {y} is {sum}"); } } } Methods with no Example: using System; Argument and with namespace FunctionDemo { Return Type class Program { static void Main(string[] args)  When a method has no arguments, it receives no data from the calling { method but returns a value. int Result=Sum(); Console.WriteLine($"Sum is {Result}"); Console.ReadKey(); } static int Sum() { int x = 10; int y = 20; int sum = x + y; return sum; } } }  Example: Methods with using System; namespace FunctionDemo Argument and no { Return Type class Program { static void Main(string[] args) {  When a method has arguments, it int x = 10, y = 20; receives data from the calling Sum(x, y); method but does not return any value. Console.ReadKey(); } static void Sum(int x, int y) { int sum = x + y; Console.WriteLine($"Sum is {sum}"); } } }  Example: Methods with using System; namespace FunctionDemo Argument and with { class Program Return Type { static void Main(string[] args) { When a method has arguments, it receives data from the calling method int x = 10, y = 20; and does return some value. int Result = Sum(x, y); Console.WriteLine($"Sum is {Result}"); Console.ReadKey(); } static int Sum(int x, int y) { int sum = x + y; return sum; } } } Call By Value and Call By Reference in C#  Example: Call By Value using System; public class Example {  In Call by Value, a copy of the public static void Main(string[] args) { actual value is passed to the int number = 10; method. Console.WriteLine("Before Call by Value: " + number); // Output: 10  The method works with this copy, so any changes made inside the method do not affect the original // Call by Value value. ModifyValue(number);  This is the default way of passing parameters in C#. Console.WriteLine("After Call by Value: " + number); // Output: 10 (No change) }  In this example, When we change num to 20, it only changes the static void ModifyValue(int num) { copy, not the original number. Output: number remains 10 outside num = 20; // This change does not affect the original value the method because the original value wasn’t modified. } }  Call by Example: using System; Reference public class Example {  In Call by Reference, public static void Main(string[] args) { a reference (or int number = 10; memory address) of Console.WriteLine("Before Call by Reference: " + number); the variable is passed // Output: 10 to the method. This allows the method to // Call by Reference work with the original value, so any changes ModifyValue(ref number); made inside the method do affect the Console.WriteLine("After Call by Reference: " + number); original variable. // Output: 20 (Changed) }  In this example, the ref keyword is used to pass the variable static void ModifyValue(ref int num) { number by reference. num = 20; // This change affects the original value When num is changed } to 20, the original } number is also changed.  Example: Recursion using System; public class RecursionExample { public static void Main(string[] args) {  Recursion is a // Calculate the factorial of 5 programming technique int number = 5; where a method calls int result = Factorial(number); itself to solve a smaller instance of the same Console.WriteLine("Factorial of " + number + " is: " + result); problem. }  It breaks down a // Recursive method to calculate factorial problem into simpler static int Factorial(int n) { sub-problems until it if (n == 1) { reaches a base case (a // Base case: when n is 1, return 1 condition where the recursion stops). return 1; } else { // Recursive case: n * factorial of (n-1) return n * Factorial(n - 1); } } } Scope of a Variable  The scope means the lifetime of that variable. It means the variable can only be accessed or visible within its scope.  The scope of variables can be defined with their declaration, and variables are declared mainly in two ways:  Global Variable: Outside of all the functions  Local Variable: Within a function block  Example Global Variable class Program { static int globalVar = 20; // Global variable  Global variables are static void Main(string[] args) { those variables which are declared outside of Console.WriteLine("Initial value: " + globalVar); all the functions or // Output: 20 block and can be ChangeValue(); // Modifying globalVar accessed globally in a Console.WriteLine("After change: " + globalVar); program. // Output: 50  Once we declare a } global variable, its value can be varied as used with different static void ChangeValue() { functions. globalVar = 50; // Changes the value stored in memory } }  Example Local using System; class StudentDetails { Variable // Method public void StudentAge() {  Variables that are declared // local variable age within or inside a block or method or constructor are known int age = 0; as Local variables. age = age + 10;  These variables are created when Console.WriteLine("Student age is : " + age); the block is entered or the function is called and destroyed } after exiting from the block or // Main Method when the call returns from the function. public static void Main(String[] args)  These variables can only be { accessed within the function in // Creating object which they are declared. StudentDetails obj = new StudentDetails(); // calling the function obj.StudentAge(); } } Thank You Any Questions ? 23