C#: Statements and Methods Based on slides by Joe Hummel.

C#: Statements and Methods

Based on slides by Joe Hummel

2UCN Technology: Computer Science – 2014

Contents

“With regards to programming statements and methods, C# offers what you would come to expect from a modern OOPL…”

• Statements• Methods


Part 1

• Statements


Statements in C#

• Assignments• Sub routines and functions• Conditionals

– if, switch• Iteration

– for, while, do-while• (Uncontrolled) Control Flow

– return, break, continue, goto


Examples

x = obj.foo();

if (x > 0 && x < 10) count++;else if (x == -1) ...else { ...}

while (x > 0){ ...

x--;} for (int k = 0; k < 10; k++)

{ ...}


Other Statements

• C# also includes…– iteration over a data structure (Collection) using foreach– namespace imported using using


foreach

• Specialised foreach loop for sweeping through collections, e.g. array– Reduces the risk for indexing errors– Allows only read only access to elements

int[] data = { 1, 2, 3, 4, 5 };int sum = 0;

foreach (int x in data){ sum += x;}

foreach

type value collection


using

• using directive provides access to classes in a namespace without pre-fixing

// before

Workshop.Customer c;c = new Workshop.Customer("joe hummel", 94652);

//after

using Workshop;

Customer c;c = new Customer("joe hummel", 94652);

namespace Workshop{ public class Customer { . . . }

public class Product { . . . }}


Example

• using directives in the top of the file

/* main.cs */

using System;using Workshop;

public class App{ public static void Main() { Customer c; c = new Customer("joe hummel", 94652); Console.WriteLine( c.ToString() ); }}

namespace Workshop{ public class Customer { . . . }

public class Product { . . . }}


Part 2

• Methods…


Types of methods

• Classes may define 2 types of methods:– instance– static

• Instance methods can only be applied to instances (objects) of the class. So an object must be created before the method can be used.

• Static methods may be called using the class name


Example

• The Array class in FCL– fully-qualified name is System.Array

namespace System{ public class Array { public int GetLength(int dimension) { ... }

public static void Sort(Array a) { ... }

. . .

}}

instance method(no static modifier)

static method(static modifier)


Method call

• Method call (Array class):

/* main.cs */

using System;

public class App{ public static void Main() { int[] data = { 11, 7, 38, 55, 3 }; Array.Sort(data);

for (int i=0; i<data.GetLength(0); i++) Console.WriteLine(i + ": " + data[i]); }}


Other static methods that may come handy…

using System;

public class Calculator{ public static void Main() { string input, output; int a, b, sum;

Console.Write("Enter first integer: "); input = Console.ReadLine(); a = Convert.ToInt32(input);

Console.Write("Enter second integer: "); input = Console.ReadLine(); b = Convert.ToInt32(input);

sum = a + b; output = String.Format("{0} + {1} = {2}", a, b, sum); Console.WriteLine(output); }}

• Adding two integers and printing the sum:


Summing Up

• All the usual statements (known from Java), and a few new ones– assignment, if, for, while, foreach, using

• Two types of methods– instance methods, needs an object– static methods, may be called on the class

C#: Statements and Methods Based on slides by Joe Hummel.

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Transcript of C#: Statements and Methods Based on slides by Joe Hummel.