Difference between revisions of "OOP Class2"

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The Assignment operator in c# is the '=' sign. You can assign variables like this...
The Assignment operator in c# is the '=' sign. You can assign variables like this...We'll learn more about operators later.
We'll learn more about operators later.
other ways to do it
other ways to do it

Revision as of 01:56, 13 September 2016

Posting home work and website

review Posting homework to moodle

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/en-us/library/ms836794.aspx



Common Language Runtime


organizing classes with hierarchy


reserved system word


MicroSoft Intermediary Language


Just In Time compilation @ first run

Everything is an Object

In c# everything is an object. And all objects inherit from the object class.

See object in the classbrowser

Since all objects inherit from the object class they all have some the basic functionality like a method called ToString();

See the source for object.cs from mono

Basic Data Types

C# is a strongly typed language. This means every object in C# must be declared to be of a specific type. All of c# basic varible type inherit from System.Object

Variable Types

.NET 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 equate to integer values, or 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; //declares a vaiable of type int
string myString;  //declares a vaiable of type string


Initialization actually sets the variables value

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

Initialization uses the assignment operator to set the value of a variable


The Assignment operator in c# is the '=' sign. You can assign variables like this...


The Assignment operator in c# is the '=' sign. You can assign variables like this...We'll learn more about operators later.

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'

Compiler Errors

  helloError4.cs(10,31): error CS0165: Use of unassigned local variable 'UsedBeforeInit'
  file            Line        .Net Framework error # and description

Csharp warning CS0168: The variable 'NeverUsed' is declared but never used

UsedBeforeInit.cs - example of misused variable
UsedBeforeInit_Fixed.cs - 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

Variable Names

Variable should be named with meaningful names.

for exmaple

z = x * y;

does not convey any meaning


distance = speed * time;

does convey meaning. If varibales are named properly it can make your code mush easier to read.

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, IntVarName

Use on method names method names.

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

ie... camelNotation, intVarName

use for variable names

Other Coding Techniques and practices

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


Strings are an object in c#

String concatenation

+ is also used to concatenate strings

If you have two string that you want to combine into one string you can concatenate them. Or use the super jedi .net method String.Format method

<csharp>//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 + ".");

string notherCoolString = "another " + coolString + " string."; Console.WriteLine(notherCoolString);

Console.WriteLine(String.Format("In Line formating of '{0}'", notherCoolString));


will output (remember \n is a new line)

    Super string theory!!!!
    Is really cool.
    another cool string.
    In Line formating of 'another cool string.'

Escape Sequences

The backslash character is used as a string escape sequence. It will escape the next character and change it's meaning. For example \" with output a ", \n with out put a newline and \\ with output a single \.

String Functions in csharp

To Upper method returns a string that only has upper case letters

string strName = "jeff";

will write JEFF

string strName = "Jeff";

will write jeff

string strName = "jMeyers";
string strNamej = "john jacob jingleheimer Schmidt";

strName = strName .Replace("j" , "J");
strNamej =  strNamej.Replace("j" , "J");

strName will be "JMeyers" strName will be "John Jacob Jingleheimer Schmidt"


Make Our Own String function

protected static void WriteColorFull(string s)
            //Save current console color so we can restore it when we are done
            //We don't want to leave the console with a random color
            ConsoleColor originalConsoleColor = Console.ForegroundColor;

            for (int index = 0; index < s.Length; index++)

                Console.ForegroundColor = mycolors[(mycolors.Length + index) % mycolors.Length];   //Rotate through colors
                Console.Write(s[index]);    //Write the current letter from the string


            //Restore Console
            Console.ForegroundColor = originalConsoleColor;


        //An array of console colors
        private static ConsoleColor[] mycolors =

Short Assignment

  Short in class Assignment
  In class assignment 10-15 mins
  Build a c# console app (remember to take a top down aproach start small with something you know maybe start with hello world)
   * 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

Top down development with comments topdown.aspx

Fully implemented Console adding program add.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace Hello
    class Program
        static void Main(string[] args)
            Console.WriteLine("Super Cool Calculatorizer");

            //Declare two variables
            int intOne;
            int intTwo;
            int intSum;

            //intialize the two variables
            intOne = 47;
            intTwo = 2;

            //Lets test the values
            Console.Write("Enter a integer: ");
            intOne = int.Parse(Console.ReadLine());     //set the value of intOne 
                                                        //to what was typed in the console
            Console.Write("Enter another integer: ");
            intTwo = int.Parse(Console.ReadLine());     //int.Parse attempts to parse a string
                                                        //and convert it to an int

            intSum = intOne + intTwo;

            Console.WriteLine("intTwo + intTwo =  " + intSum);




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

OOP Arrays

csharp Arrays

Arrays are groups of variables of the same type Syntax

<csharp>type [] identifier</csharp>

single dimension arrays

<csharp>string [] aryNames = new string[3];

aryNames [0] = "Joe"; aryNames [1] = "Mike"; aryNames [2] = "Alice";</csharp>

Example single dimensions array singleArrray.aspx singleArray.cs

multi dimension arrays

<csharp>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";</csharp>

Example multi dimensions array multiArrray.aspx

jagged arrays

<csharp>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";</csharp>

Example jagged array jaggedArrray.aspx jaggedArray.cs

even more array samples

<csharp>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]); } }</csharp> moreArrys.cs

Simple Branching



if (expression)
    // statement
if (expression) {
    // statements
    // statements
if (expression) {
    // statements
    // statements
else {
    // statements


  • Learning c#
  • Chapter 5, Chapter 6


1.Create a simple text game that asks three questions and sets three variables. There should be a fourth variable that counts the number of correct answers. The program should run in the console and use:

  • Console.WriteLine
  • Console.ReadLine
  • ints, strings and ifs

Analysis of Homework Project

  • On very structured programs like this one analysis is quite easy
    • Start by identifying the steps
    • Add Pseudocode as c# comments for each step
    • Fill in the real syntax for each step and compile each time to make sure nothing breaks (I like to call this baby steps and I like to use this technique whenever I'm trying to implement something that is completely new to me)

The pseudocode might look something like

using System;
namespace HelloVariables
    class ThreeQuestions
        public static void Main()
            Console.WriteLine("3 Questions");
            //A simple game that asks three questions and checks the answers. If the question is answered correctly we will award 1 point

            //Declare Variables
            //Ask Question 1

            //Read Answer

            //Check Answer and add 1 to points is correct

            //Repeat with Questions 2 and 3

            //Display Percent Correct

2. Broken Toaster Week 2 in Moodle

3. Watch http://www.microsoftvirtualacademy.com/training-courses/c-fundamentals-for-absolute-beginners

  • 05 Quick Overview of the Visual C# Express Edition IDE 30 Mins
  • 06 Declaring Variables and Assigning Values Duration 28 Mins
  • 07 Branching with the if Decision Statement and the Conditional Operator 19 Mins

Download the BrokenToaster project and fix the errors so that it creates the correct output. You may change any source you need to create the output. The program flow inputs and outputs should remain in tact. Points will be awarded modifications made to achieve the correct interaction and output.


This text will be replaced