C# Development 
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                                    
                                             Rob Miles  
                                                    
                                             2008-2009 
                                                    
                                                    
                             Department of Computer Science 
                                        University of Hull 
           
          
         Contents 
                     Introduction....................................................................................................................... 11 
                         Welcome ............................................................................................................. 11 
                         Reading the notes................................................................................................ 11 
                         Getting a copy of the notes ................................................................................. 11 
                 Computers                                  12 
                     An Introduction to Computers .......................................................................................... 12 
                         Hardware and Software ...................................................................................... 12 
                     Data and Information ........................................................................................................ 13 
                         Data Processing .................................................................................................. 13 
                         Programmer’s Point:At the bottom there is always hardware ............................. 14 
                 Programming Languages                      15 
                     What is Programming? ..................................................................................................... 15 
                         From Problem to Program .................................................................................. 15 
                         Programmer’s Point:The specification must always be there ............................. 16 
                     A Simple Problem ............................................................................................................. 16 
                         Specifying the Problem ....................................................................................... 16 
                         Programmer’s Point:metadata is important ......................................................... 17 
                         Programmer’s Point:Good programmers are good communicators .................... 19 
                     Programming Languages .................................................................................................. 19 
                         Programmer’s Point:The language is not that important..................................... 20 
                 C#                                         20 
                     A look at C# ...................................................................................................................... 20 
                         Dangerous C ....................................................................................................... 20 
                         Programmer’s Point:Computers are always stupid ............................................. 21 
                         Safe C# ............................................................................................................... 21 
                         C# and Objects ................................................................................................... 21 
                         Making C# Run .................................................................................................. 21 
                         Creating C# Programs ........................................................................................ 22 
                         The Human Computer ........................................................................................ 22 
                         Programmer’s Point:Great programmers debug less .......................................... 22 
                     What Comprises a C# Program? ....................................................................................... 22 
                         Controlling the Compiler .................................................................................... 23 
                         Storing the Data .................................................................................................. 23 
                         Describing the Solution ...................................................................................... 23 
                         Identifiers and Keywords .................................................................................... 23 
                 A First C# Program                         24 
                     The Program Example ...................................................................................................... 24 
                         using System; ............................................................................................. 24 
                         class GlazerCalc ...................................................................................... 25 
                         static.............................................................................................................. 25 
                         void .................................................................................................................. 25 
                         Main .................................................................................................................. 25 
                         () ....................................................................................................................... 25 
                                                               i 
          
                         { .......................................................................................................................... 26 
                         double.............................................................................................................. 26 
                         width, height, woodLength, glassArea ...................................... 26 
                         Programmer’s Point:Know where your data comes from ................................... 26 
                         ; ......................................................................................................................... 26 
                         string widthString, heightString; ............................................. 27 
                         widthString = ............................................................................................. 27 
                         Console. ......................................................................................................... 27 
                         ReadLine ......................................................................................................... 27 
                         () ....................................................................................................................... 27 
                         ; ......................................................................................................................... 28 
                         width = ........................................................................................................... 28 
                         double. ........................................................................................................... 28 
                         Parse ................................................................................................................ 28 
                         (widthString); .......................................................................................... 28 
                         heightString = Console.ReadLine(); height = 
                         double.Parse(heightString);............................................................ 29 
                         woodLength = 2*(width + height)*3.25 ; ................................. 29 
                         glassArea = 2 * ( width * height ) ; ...................................... 29 
                         Console.WriteLine ................................................................................... 29 
                         ( ......................................................................................................................... 29 
                         "The length of the wood is " ......................................................... 29 
                         + ......................................................................................................................... 29 
                         woodLength .................................................................................................... 30 
                         + " feet" ...................................................................................................... 30 
                         ) ......................................................................................................................... 30 
                         ; ......................................................................................................................... 31 
                         } ......................................................................................................................... 31 
                         } ......................................................................................................................... 31 
                         Programmer’s Point:Program layout is very important ...................................... 31 
                         Punctuation ......................................................................................................... 31 
                 Manipulating Data                          32 
                     Variables and Data ............................................................................................................ 32 
                     Types of Variables ............................................................................................................ 32 
                         Storing Numbers ................................................................................................. 32 
                         Storing integer values ......................................................................................... 33 
                         Programmer’s Point:Check your own maths....................................................... 33 
                         integer literal values ............................................................................................ 34 
                         Storing real values .............................................................................................. 34 
                         real literal values ................................................................................................. 34 
                         Programmer’s Point:Simple variables are probably best .................................... 35 
                         Storing Text ........................................................................................................ 35 
                         char variables ...................................................................................................... 35 
                         char literal values ................................................................................................ 35 
                         string variables .................................................................................................... 36 
                         string literal values .............................................................................................. 37 
                         bool variables ..................................................................................................... 37 
                         bool literal values ............................................................................................... 37 
                         Programmer’s Point:Think about the type of your variables .............................. 37 
                     Identifiers .......................................................................................................................... 38 
                         Programmer’s Point:Think about the names of your variables ........................... 38 
                     Giving Values to Variables ............................................................................................... 39 
                         Expressions ......................................................................................................... 39 
                     Changing the Type of Data ............................................................................................... 40 
                         Widening and Narrowing ................................................................................... 40 
                         Casting ................................................................................................................ 41 
                                                               ii 
          
                     Types of Data in Expressions............................................................................................ 42 
                         Programmer’s Point:Casts can add clarity .......................................................... 43 
                     Programs and Patterns ...................................................................................................... 43 
                 Writing a Program                          44 
                     Software as a story ............................................................................................................ 44 
                         Comments ........................................................................................................... 45 
                         Programmer’s Point:Don't add too much detail .................................................. 45 
                     Program Flow ................................................................................................................... 45 
                         Conditional Execution - if .................................................................................. 46 
                         Conditions and Relational Operators .................................................................. 46 
                         Combining Logical Operators ............................................................................ 48 
                         Programmer’s Point:Break down your conditions .............................................. 48 
                         Lumping Code Together ..................................................................................... 48 
                         Metadata, Magic Numbers and const ................................................................. 49 
                     Loops ................................................................................................................................ 50 
                         Programmer’s Point:Don't be clever/stupid ........................................................ 53 
                         Breaking Out of Loops ....................................................................................... 53 
                         Programmer’s Point:Be careful with your breaks ............................................... 53 
                         Going back to the top of a loop .......................................................................... 54 
                         More Complicated Decisions ............................................................................. 54 
                         Programmer’s Point:Get used to flipping conditions .......................................... 54 
                         Complete Glazing Program ................................................................................ 54 
                     Operator Shorthand ........................................................................................................... 55 
                         Statements and Values ........................................................................................ 56 
                         Programmer’s Point:Always strive for simplicity ............................................... 57 
                     Neater Printing .................................................................................................................. 57 
                         Using Placeholders in Print Strings .................................................................... 57 
                 Methods                                    59 
                     Methods So Far ................................................................................................................. 59 
                         Method and Laziness .......................................................................................... 59 
                         Parameters .......................................................................................................... 60 
                         Return values ...................................................................................................... 60 
                         A Useful Method ................................................................................................ 60 
                         Programmer’s Point:Design with methods ......................................................... 61 
                         Method Limitations ............................................................................................ 61 
                         Programmer’s Point:Document your side-effects ............................................... 63 
                         Programmer’s Point:Languages can help programmers...................................... 63 
                         Method Libraries ................................................................................................ 64 
                         Programmer’s Point:Always consider the failure behaviours ............................. 64 
                     Variables and Scope ......................................................................................................... 64 
                         Scope and blocks ................................................................................................ 65 
                         Nested Blocks ..................................................................................................... 65 
                         For loop local variables ...................................................................................... 66 
                         Programmer’s Point:Plan your variable use ........................................................ 66 
                 Arrays                                     66 
                     Why We Need Arrays ....................................................................................................... 66 
                         Array Elements ................................................................................................... 67 
                         Array Element Numbering .................................................................................. 68 
                         Large Arrays ....................................................................................................... 68 
                         Managing Array Sizes ........................................................................................ 68 
                         Creating a Two Dimensional Array .................................................................... 69 
                         More than Two Dimensions ............................................................................... 69 
                         Programmer’s Point:Keep your dimensions low ................................................ 69 
                                                              iii