OOP Class2

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Revision as of 23:39, 10 January 2006 by Jeff (talk | contribs) (Basic Data Types)
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C# fundamentals

Questions from week 1 reading. discussion

Some pages comparing c# to other languages

A Comparative Overview of C# http://genamics.com/developer/csharp_comparative.htm

C# and Java: Comparing Programming Languages http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dncenet/html/tchCJavaComparingProgrammingLanguages.asp

Basic Data Types

C# is a strongly typed language. This means every object in C# must be declared to be of a specific type. Variable Types

Type Size in Bytes .Net Type Description
byte 1 Byte Unsigned (0-255)
char 2 Char Unicode Characters ascii unicode and other
bool 1 Boolean True of False (note c# boolean values do not eqaute to interget value True != (read as is not equal to) 1 and False != 0)
sbyte 1 SByte Signed integers(-128 to 127)
short 2 Int16 Signed integers(-32,768 to 32,767)
ushort 2 UInt16 Unsigned integers(0 to 65,535)
int 4 Int32 Signed integers(-2,147,483,648 to 2,147,483,647)
uint 4 UInt32 Unsigned integers(0 to 4,294,967,295)
float 4 Single fixed-precision up to 7 digits. Floating point number ( 1.5 x 10-45 to 3.4 x 1038 )
double 8 Double fixed-precision up to 16 digits. Floating point number ( 5.0 x 10-324 to 1.7 x 10308 )
decimal 12 Decimal fixed-precision up to 28 digits. Typically used for financial calculations. Required the suffix "m" or "M"
long 8 Int64 Signed integer ( -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807)
ulong 8 UInt64 Unsigned integer (0 to 18,446,744,073,709,551,615 )

Variables must be declared with an identifier and then initialized.


Declaration sets aside a named section of memory the is the proper size to hold the declared type. At this point the variable contains nothing.

// declare a variable int firstInt; string myString;


Initialization actually sets the variables value

// initialize the variable firstInt = 1; myString = "Hello!";

other ways to do it

// declare some variables int secondInt, thirdInt, fourthInt; secondInt = 2; thirdInt = 3; fourthInt = 4;

//declare and initialize variables in one line int myNegativeInt = -2147483648;

In c# variables cannot be used unil they are initalized. For example

   int UsedBeforeInit;

will produce

helloError4.cs(10,31): error CS0165: Use of unassigned local variable


UsedBeforeInit.aspx - web example of misused variable source UsedBeforeInit_Fixed.aspx - all beter now source

More examples of built in types 1x1.cs C# intrinsic types from Learn-C-Sharp. variable.aspx - example from book aspx page View Source variable2.aspx = example from book errors View Source

Naming conventions

Name variables intelligently. Name variables with names that have meaning.

Hungarian Notation Hungarian notation id a popular notation system used be many C, C++ and VB programmers. It was originally devised in Charles Simonyi's doctoral thesis, "Meta-Programming: A Software Production Method." Hungarian notation specifies that a prefix be added to each variable that indicated that variables type. It also specifies sometimes adding a suffice to clarify variables meaning. In the early 1980's Microsoft adopted this notation system.

ie... intHitCounter, intHitsPerMonthMax Hungarian Notation - Charles Simonyi Microsoft

PascalNotation Capitalize first Letter and then the first letter on each word. ie... PascalNotation

Use on method names method names.

camelNotation Lower case first letter and then capitalize the first letter of each word ie... camelNotation

use for variable names Other Coding Techniques and practices Microsoft - Coding Techniques and Programming Practices IBM Best Practices for Programming in C GNU Coding Standards GNU Naming conventions More Types


ECMA-334 Operators and punctuators

C# uses the equals = sign for Assignment

int myVar = 15;			 //sets the value of myVar to 15

Mathematical Operators

Operator Description
* multiplication
/ division
% modulus remainder Ask Dr.Math What is Modulus?

Increment Decrement Operators

Operator Description
+ increment same as foo = foo + 1
-- decrement same as foo = foo - 1
= calculate and reassign addition
-= calculate and reassign subtraction
*= calculate and reassign multiplication
/= calculate and reassign division
%= calculate and reassign modulus
y= x++ assignment prefix y is assigned to x and then x in incremented
y= ++x assignment postfix x is incremented and then assigned to y

operator Precedence Evaluated First

   * ++,--,unary-
   * *,/,%
   * +,-

Evaluated Last

   * =,+=,-=,*=,etc

+ is also used to concatenate strings

    //Create a string and set it's value to "cool."
    string coolString = "cool";
    //Do some concatenations and make it super cool
    Console.WriteLine ("Super " + "string " + "theory!!!\n" + "Is really " + coolString + ".");

will output (remember \n is a new line)

    Super string theory!!!!
    Is really cool.

Short in class Assignment In class assignment 10-15 mins Build a c# console app (remember to take a takedown aproach start small with somethin you know)

   * Declare and initialize two integers
   * Display their values using Console.WriteLine
   * Declare a third integer and initialize it with the sum of the first two integers
   * Output the value of the third integer

Once the console application is done convert it to work on a web page using Response.Write instead of Console.WriteLine

Top down development with comments /infod/jeff/classsource/class2/topdown.aspx Fully implemeted Console adding program /infod/jeff/classsource/class2/add.cs Conversions and Casting

Casting is the process of converting form one type of object to another, There are two Conversion types in C# implicit and explicit. Implicit conversion is handled by the compiler and requires no extra work. Implicit conversion is only possible if the new data type can hold the old data type with out any data loss. explicit conversion forces on datatype into another even if it doesn't fit. It is up to the programmer to define explicit casts. implicit conversion

int intNumber = 1000; long lngNumber; lngNumber = intNumber;

int Number1= 6; int Number2= 5; int Number3 = Number1 / Number2; //Number3 == 1

explicit conversion

long lngNumber = 1000; int intNumber; intNumber = (int)lngNumber;

int Number1= 6; int Number2= 5; double Number3 = (double)Number1 / (double)Number2; //Number3 == 1.2


Constants are datatypes that will be assigned a value that will be constant thought the executing of the code. You cannot change constants once they have been assigned a value. syntax

const type identifier = value;


const int freezingPoint = 32; const int freezingPointMetric = 0; const float pi = 3.141592


Arrays are groups of variables of the same type Syntax

type [] identifier

single dimension arrays

 		string [] aryNames = new string[3];
 		aryNames [0] = "Joe";
 		aryNames [1] = "Mike";
 		aryNames [2] = "Alice";

Example single dimensions array singleArrray.aspx Source multi dimension arrays

		string [,] aryNames = new string[3,3];

aryNames [0,0] = "Joe"; aryNames [0,1] = "Schmoe"; aryNames [0,2] = "111 111-1111"; aryNames [1,0] = "Mike"; aryNames [1,1] = "Orbinawitz"; aryNames [1,2] = "222 222-2222"; aryNames [2,0] = "Mary"; aryNames [2,1] = "Alice"; aryNames [2,2] = "333 333-3333";

Example multi dimensions array multiArrray.aspx Source jagged arrays

string [][] aryNames = new string[3][];

aryNames[0] = new string[2]; aryNames[1] = new string[4]; aryNames[2] = new string[3];

aryNames [0][0] = "John"; aryNames [0][1] = "Doe";

aryNames [1][0] = "James"; aryNames [1][1] = "Bond"; aryNames [1][2] = "007"; aryNames [1][3] = "License to kill";

aryNames [2][0] = "Mary"; aryNames [2][1] = "Alice"; aryNames [2][2] = "Im not a number im a free woman";

Example jagged array jaggedArrray.aspx Source even more array samples

using System;

class Array { public static void Main() { //array of ints int[] myInts = {5,10,15}; Console.WriteLine("array of ints:"); Console.WriteLine( "myInts[0]: {0}, myInts[1]: {1}, myInts[2]:{2}" ,myInts[0],myInts[1],myInts[2]);

//jagged array of bools bool[][] myBools = new bool[2][]; myBools[0] = new bool[2]; myBools[1] = new bool[1];

myBools[0][0] = true; myBools[0][1] = false; myBools[1][0] = true; Console.WriteLine("jagged array of bools:"); Console.WriteLine( "myBools[0][0]: {0}, myBools[1][0]: {1}", myBools[0][0], myBools[1][0]);

//multi-dimensional array of doubles double[,] myDoubles = new double[2,2]; myDoubles[0, 0] = 3.147; myDoubles[0, 1] = 7.157; myDoubles[1, 1] = 2.117; myDoubles[1, 0] = 56.00138917; Console.WriteLine("multi-dimensional array of doubles:"); Console.WriteLine("myDoubles[0, 0]: {0}, myDoubles[1, 0]: {1}", myDoubles[0, 0], myDoubles[1, 0]);

//array of strings string[] myStrings = new string[3]; myStrings[0] = "Joe"; myStrings[1] = "Matt"; myStrings[2] = "Robert"; Console.WriteLine("array of strings:"); Console.WriteLine("myStrings[0]: {0}, myStrings[1]: {1}, myStrings[2]: {2}", myStrings[0], myStrings[1], myStrings[2]); } }


Lightweight alternatives to classes. Structs do not support inheritance or destructors. Don't worry if you don't understand structs yet it hard cuz the book teaches them before classes. We will talk more about stucts after we talk about classes Syntax

[ attributes] [access-modifiers] struct identifier [:interface-list {struct members}

struct Dog {

public string name;
public string weight;
public int age;



Enumerators are used to set predefined list of named constants. Syntax

[ attributes] [modifiers] enum identifier [:base-type {enumerator-list};

 //An enumerator for ServingSizes at BK
 enum ServingSizes : uint
   Small = 0,
   Regular = 1,
   Large = 2,
   SuperSize = 3
 //another more usefull example
 // forced sequence to start  
 // from 1 instead of 0 (default)
 enum Months 
   January = 1, February , March, April ,
   May , June , July , August , Sept , Oct , Nov , Dec 

Web Forms

Http is a staless protocol. There is mo mechanism built in to the protocol that allows the server to remeber clients or requests. An http simply responds to http verbs GET, POST, PUT, DEL, TRACE etc. contained in RFC 2068 HTTP/1.1 Introduction to ASP .NET and Web Forms - uses VB.Net

Old html forms post information using forms in 2 ways with a get or a post http request. Get

Get send information to the server using the URI. Limited to 1024 character in some browsers and servers.

<form action="class2.aspx" method="get"> FirstName: <input type="text" name="FirstName">
LastName: <input type="text" name="LastName">
<input type="submit" value="Submit"> </form>

FirstName: LastName: Post - Post posts the varibles in the HTTP Header.

<form action="class2.aspx" method="post"> FirstName: <input type="text" name="FirstName">
LastName: <input type="text" name="LastName">
<input type="submit" value="Submit"> </form>

FirstName: LastName: Header Name Value HttpMethod GET Connection keep-alive Keep-Alive 300 Accept text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 Accept-Encoding gzip,deflate Accept-Language en-us,en;q=0.5 Cookie ASP.NET_SessionId=0cjrrijphnnknkvjth5mdw55 Host imdev Referer http://imdev/infod/jeff/ User-Agent Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.12) Gecko/20050915 Firefox/1.0.7

HTML Forms Example HTML Forms htmlForms.html Source Examples of Web Forms ASP.NET Server Controls

Example server controls serverControls.aspx Source HomeWork Learning c# Chapter 6, Chapter 7 47-84

Read Chapter 03 Read Chapter 04 pg 59-190 LearnC-Sharp tutorial 1 Data Types - Learnc# is DED

Build an aspx page that can post data and catch the results like PostandCatch.aspx simple or PostCatch_com .aspx -tougher

   HTML form page                          1 pt  
   HTML (only html no c# or .net) page that demostrates an html form using
   at least 3 html form elements.    
   HTML post to aspx catch                 1 pt
   Use your previously created html FORM tp post info to an asps page that catches
   all the variables and displays them.
   An aspx webform page that posts to itself   2 pts    
   An aspx web form that posts information to itself and displays the results.

Build a console application

Variable Types and Casting 4pts 1 extra credit Build a console application that declares and initializes three integers with watever values you like Display these integers in the console Cast the intergers into three floats Display the floats Cast the integers into three strings Display the strings Put the strings into an array Display the array

extra credit use an enumerator to change word stings into ints ie "one" = 1 "two" = 2

codetoad.com ASP.NET : HTML Server Controls aspalliance.com - ASP.NET Syntax for Web Server Controls Next week Quiz on weeks 1 and 2

Chapter 3 Source checkpage.aspx View Source listpage.aspx View Source listpage2.aspx View Source listpage2_fixed.aspx -jeff View Source

labelcontrol.aspx View Source listpage2_fixed.aspx View Source radiopage.aspx View Source textboxpage.aspx View Source Chapter 4 Source variable.aspx View Source variable2.aspx View Source tax.aspx View Source textboxarray.aspx View Source conversion.aspx View Source other sources server-controls from professional ASP.NET Links A Comparative Overview of C# Introduction to ASP .NET and Web Forms - uses VB.Net Microsoft - Coding Techniques and Programming Practices IBM Best Practices for Programming in C GNU Coding Standards GNU Naming conventions RFC 2068 HTTP/1.1 Review