Advanced Programming C# Introduction

Application Types Console Application Windows Application Service Has standard streams (out, in, err) GUI can be added manually Windows Application GUI based No standard streams (out, in, err) Main thread is shared by the GUI message pump & your code Service Main thread is commandeered by the SCM No GUI

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Windows Application

Simple Program – console application // A first program in C#. using System; class Welcome1 { static void Main( string[] args ) Console.WriteLine( "Welcome to C# Programming!" ); } }

Constructions of Note using namespace class like import in Java: bring in namespaces namespace disambiguation of names like Internet hierarchical names and C++ naming class like in C++ or Java single inheritance up to object

Constructions of Note static void Main() Console.Write(Line) Defines the entry point for an assembly. Four different overloads – taking string arguments and returning int’s. Console.Write(Line) Takes a formatted string: “Composite Format” Indexed elements: e.g., {0} can be used multiple times only evaluated once {index [,alignment][:formatting]}

Common Type System (CTS) From MSDN

Atomic Data

Simple Program: Add Integers Primitive data types Data types that are built into C# string, int, double, char, long Console.ReadLine() Used to get a value from the user input Int32.Parse() Used to convert a string argument to an integer Allows math to be preformed once the string is converted

Built-in Types C# predefined types The “root” object Logical bool Signed sbyte, short, int, long Unsigned byte, ushort, uint, ulong Floating-point float, double, decimal Textual char, string Textual types use Unicode (16-bit characters)

Types Unified Type System Value types Directly contain data Cannot be null Reference types Contain references to objects May be null In C# you have value types that directly hold the data on the stack and reference types that keeps a reference on the stack, but allocates the real memory on the heap. Also have pointer types in unsafe code. Will discuss those in Part 2. int i = 123; string s = "Hello world"; 123 i s "Hello world"

Programs Write a C program to read three integer numbers and find their average.

Predefined Types Value Types All are predefined structs Signed sbyte, short, int, long Unsigned byte, ushort, uint, ulong Character char Floating point float, double, decimal Logical bool

Predefined Types Integral Types C# Type System Type Size (bytes) Signed? sbyte System.Sbyte 1 Yes short System.Int16 2 int System.Int32 4 long System.Int64 8 byte System.Byte No ushort System.UInt16 uint System.UInt32 ulong System.UInt64

Predefined Types Floating Point Types Follows IEEE 754 specification Supports ± 0, ± Infinity, NaN C# Type System Type Size (bytes) float System.Single 4 double System.Double 8

Predefined Types decimal 128 bits Essentially a 96 bit value scaled by a power of 10 Decimal values represented precisely Doesn’t support signed zeros, infinities or NaN C# Type System Type Size (bytes) decimal System.Decimal 16

Predefined Types bool Represents logical values Literal values are true and false Cannot use 1 and 0 as boolean values No standard conversion between other types and bool Eliminating implicit conversions between numbers and bool can help find subtle bugs. C# Type System Type Size (bytes) bool System.Boolean 1 (2 for arrays)

Predefined Types char Represents a Unicode character Literals ‘A’ // Simple character ‘\u0041’ // Unicode ‘\x0041’ // Unsigned short hexadecimal ‘\n’ // Escape sequence character C# Type System Type Size (bytes) Char System.Char 2

Predefined Types string An immutable sequence of Unicode characters Reference type Special syntax for literals string s = “I am a string”; C# Type System Type Size (bytes) String System.String 20 minimum

Type System Value types Reference types Primitives int i; Enums enum State { Off, On } Structs struct Point { int x, y; } Reference types Classes class Foo: Bar, IFoo {...} Interfaces interface IFoo: IBar {...} Arrays string[] a = new string[10]; Delegates delegate void Empty();

Example Assume you work for the Alexandria Electricity company and you need a program to help you calculate the electricity bill for each customer. The program input should be the old meter reading and the new meter reading. Given that the price is 0.10 pounds per kilowatt.

Program Structure Main Method Execution begins at the static Main() method Can have only one method with one of the following signatures in an assembly static void Main() static int Main() static void Main(string[] args) static int Main(string[] args)

C# Comments Comments can be created using //… Multi-lines comments use /* … */ Comments are ignored by the compiler

Program Structure Syntax Identifiers Names for types, methods, fields, etc. Must be whole word – no white space Unicode characters Begins with letter or underscore Case sensitive Must not clash with keyword Unless prefixed with @

Identifiers: Keywords Often we use special identifiers called keywords that already have a predefined meaning in the language Example: class A keyword cannot be used in any other way All C# keywords are lowercase!

Arithmetic Arithmetic operations Asterisk (*) is multiplication Slash (/) is division Percent sign (%) is the modulus operator Plus (+) and minus (-) are the same There are no exponents

Operators Associativity Assignment and ternary conditional operators are right-associative Operations performed right to left x = y = z evaluates as x = (y = z) All other binary operators are left-associative Operations performed left to right x + y + z evaluates as (x + y) + z Use parentheses to control order

C# Keywords Words that cannot be used as variable or class names Have a specific unchangeable function within the language Example: class

C# Classes Class names can only be one word long (i.e. no white space in class name ) Class names are capitalized, with each additional English word capitalized as well (e.g., MyFirstProgram ) Each class name is an identifier Can contain letters, digits, and underscores (_) Cannot start with digits Can start with the at symbol (@)

C# Class Methods Class bodies start with a left brace ({) Class bodies end with a right brace (}) Methods Building blocks of programs The Main method Each console or windows application must have exactly one All programs start by executing the Main method Braces are used to start ({) and end (}) a method

C# Statements Anything in quotes (“) is considered a string Every statement must end in a semicolon (;)

C#

NameSpaces You import namespaces when you want to be able to refer to classes by their short name, rather than full name For example, import System.XML allows XmlDataDocument and XmlNode rather than System.XML.XmlDataDocument and System.XML.XmlNode to be in your code.

Program Structure Namespaces namespace N1 {     // N1 class C1 {   // N1.C1 class C2 {   // N1.C1.C2 }     namespace N2 {    // N1.N2 class C2 { // N1.N2.C2     } The comments show the fully qualified names. A namespace called N3.N4 is like two nested namespaces.

Program Structure Namespaces The using statement lets you use types without typing the fully qualified name Can always use a fully qualified name using N1; C1 a; // The N1. is implicit N1.C1 b; // Fully qualified name C2 c; // Error! C2 is undefined N1.N2.C2 d; // One of the C2 classes C1.C2 e; // The other one Note that it is N1.C1, not N1::C1 The using statement is scoped by the namespace and/or compilation module containing it.

Program Structure Namespaces Best practice: Put all of your types in a unique namespace Have a namespace for your company, project, product, etc. Look at how the .NET Framework classes are organized

Namespaces Partition the name space to avoid name conflict! All .NET library code are organized using namespaces! By default, C# code is contained in the global namespace To refer to code within a namespace, must use qualified name (as in System.Console) or import explicitly (as in using System; ) using System; class HelloWorld { static void Main(string[] args) Console.WriteLine(“Hello World!”); } class HelloWorld { static void Main(string[] args) System.Console.WriteLine(“Hello World!”); }

Welcome4.cs // Printing multiple lines in a dialog Box. using System; using System.Windows.Forms; class Welcome4 { static void Main( string[] args ) MessageBox.Show( "Welcome \n to \n C# \n programming!" );} }

Statements Overview Loop Statements Statement lists Block statements while do for foreach Jump Statements break continue goto return throw Exception handling try Statement lists Block statements Labeled statements Declarations Constants Variables Expression statements checked, unchecked lock using Conditionals if switch

Statements Expression Statements Statements must do work Assignment, method call, ++, --, new static void Main() { int a, b = 2, c = 3; a = b + c; a++; Console.WriteLine(a + b + c); a == 2; // ERROR! } Expression statements must do work.

Events Events are a way for an object to communicate with those that are interested in what it has to offer, like a button has a click event Interested parties use Event Handlers, which are a way of subscribing to the event

Math Class Methods The Math class Allows the user to perform common math calculations Using methods ClassName.MethodName( argument1, arument2, … ) Constants Math.PI = 3.1415926535… Math.E = 2.7182818285…

Math Class Methods

Example A motor car uses 8 liters of fuel per 100 km on normal roads and 15% more fuel on rough roads. Write a program to print out the distance the car can travel on full tank of 40 liters of fuel on both normal and rough roads.

Statements Variables and Constants static void Main() { const float pi = 3.14f; const int r = 123; Console.WriteLine(pi * r * r); int a; int b = 2, c = 3; a = 1; Console.WriteLine(a + b + c); }

Example Write a program to ask you for the temperature in Fahrenheit and then convert it to Celsius. Given: C= 5/9 (F-32) Write a program to ask you for the temperature in Celsius and then convert it to Fahrenheit.

Programs Write a program to ask a person for his height in feet and inches and then tell them his height in cms. Given that 1 foot = 30 cms and 1 inch = 2.5 cms.

Examples Write a program to ask the user for the width and length of a piece of land and then tell him how many orange trees he can grow on it. Given that each orange tree requires 4 m2.

Examples Write a program to ask the user for the radius of a circle, and then display its area and circumference.