mirror of
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549 lines
15 KiB
Markdown
549 lines
15 KiB
Markdown
---
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language: c#
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contributors:
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- ["Irfan Charania", "https://github.com/irfancharania"]
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filename: LearnCSharp.cs
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---
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C# is an elegant and type-safe object-oriented language that enables developers to build a variety of secure and robust applications that run on the .NET Framework.
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[Read more here.](http://msdn.microsoft.com/en-us/library/vstudio/z1zx9t92.aspx)
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```c#
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// Single-line comments start with //
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/*
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Multi-line comments look like this
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*/
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/// <summary>
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/// This is an XML documentation comment
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/// </summary>
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// Specify namespaces application will be using
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using System;
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using System.Collections.Generic;
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// defines scope to organize code into "packages"
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namespace Learning
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{
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// Each .cs file should at least contain a class with the same name as the file
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// you're allowed to do otherwise, but shouldn't for sanity.
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public class LearnCSharp
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{
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// A console application must have a main method as an entry point
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public static void Main(string[] args)
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{
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// Use Console.WriteLine to print lines
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Console.WriteLine("Hello World");
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Console.WriteLine(
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"Integer: " + 10 +
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" Double: " + 3.14 +
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" Boolean: " + true);
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// To print without a new line, use Console.Write
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Console.Write("Hello ");
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Console.Write("World");
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///////////////////////////////////////////////////
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// Types & Variables
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//
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// Declare a variable using <type> <name>
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///////////////////////////////////////////////////
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// Sbyte - Signed 8-bit integer
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// (-128 <= sbyte <= 127)
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sbyte fooSbyte = 100;
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// Byte - Unsigned 8-bit integer
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// (0 <= byte <= 255)
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byte fooByte = 100;
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// Short - Signed 16-bit integer
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// (-32,768 <= short <= 32,767)
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short fooShort = 10000;
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// Ushort - Unsigned 16-bit integer
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// (0 <= ushort <= 65,535)
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ushort fooUshort = 10000;
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// Integer - Signed 32-bit integer
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// (-2,147,483,648 <= int <= 2,147,483,647)
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int fooInt = 1;
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// Uinteger - Unsigned 32-bit integer
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// (0 <= uint <= 4,294,967,295)
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uint fooUint = 1;
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// Long - Signed 64-bit integer
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// (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807)
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long fooLong = 100000L;
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// L is used to denote that this variable value is of type long or ulong
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// anything without is treated as int or uint depending on size.
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// Ulong - Unsigned 64-bit integer
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// (0 <= ulong <= 18,446,744,073,709,551,615)
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ulong fooUlong = 100000L;
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// Float - Single-precision 32-bit IEEE 754 Floating Point
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// Precision: 7 digits
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float fooFloat = 234.5f;
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// f is used to denote that this variable value is of type float;
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// otherwise it is treated as double.
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// Double - Double-precision 64-bit IEEE 754 Floating Point
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// Precision: 15-16 digits
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double fooDouble = 123.4;
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// Bool - true & false
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bool fooBoolean = true;
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bool barBoolean = false;
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// Char - A single 16-bit Unicode character
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char fooChar = 'A';
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// Strings
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string fooString = "My string is here!";
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Console.WriteLine(fooString);
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// formatting
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string fooFormattedString = string.Format("Check Check, {0} {1}, {0} {1:0.0}", 1, 2);
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Console.WriteLine(fooFormattedString);
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// formatting dates
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DateTime fooDate = DateTime.Now;
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Console.WriteLine(fooDate.ToString("hh:mm, dd MMM yyyy"));
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// \n is an escaped character that starts a new line
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string barString = "Printing on a new line?\nNo Problem!";
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Console.WriteLine(barString);
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// it can be written prettier by using the @ symbol
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string bazString = @"Here's some stuff
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on a new line!";
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Console.WriteLine(bazString);
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// quotes need to be escaped
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// use \" normally
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string quotedString = "some \"quoted\" stuff";
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Console.WriteLine(quotedString);
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// use "" when strings start with @
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string quotedString2 = @"some MORE ""quoted"" stuff";
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Console.WriteLine(quotedString2);
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// Use const or read-only to make a variable immutable
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// const values are calculated at compile time
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const int HOURS_I_WORK_PER_WEEK = 9001;
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// Nullable types
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// any type can be made nullable by suffixing a ?
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// <type>? <var name> = <value>
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int? nullable = null;
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Console.WriteLine("Nullable variable: " + nullable);
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// ?? is syntactic sugar for specifying default value
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// in case variable is null
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int notNullable = nullable ?? 0;
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Console.WriteLine("Not nullable variable: " + notNullable);
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// Var - compiler will choose the most appropriate type based on value
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var fooImplicit = true;
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///////////////////////////////////////////////////
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// Data Structures
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///////////////////////////////////////////////////
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Console.WriteLine("\n->Data Structures");
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// Arrays
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// The array size must be decided upon declaration
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// The format for declaring an array is follows:
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// <datatype>[] <var name> = new <datatype>[<array size>];
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int[] intArray = new int[10];
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string[] stringArray = new string[1];
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bool[] boolArray = new bool[100];
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// Another way to declare & initialize an array
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int[] y = { 9000, 1000, 1337 };
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// Indexing an array - Accessing an element
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Console.WriteLine("intArray @ 0: " + intArray[0]);
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// Arrays are zero-indexed and mutable.
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intArray[1] = 1;
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Console.WriteLine("intArray @ 1: " + intArray[1]); // => 1
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// Lists
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// Lists are used more frequently than arrays as they are more flexible
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// The format for declaring a list is follows:
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// List<datatype> <var name> = new List<datatype>();
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List<int> intList = new List<int>();
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List<string> stringList = new List<string>();
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// Another way to declare & initialize a list
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List<int> z = new List<int> { 9000, 1000, 1337 };
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// Indexing a list - Accessing an element
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// Lists are zero-indexed and mutable.
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Console.WriteLine("z @ 0: " + z[2]);
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// Lists don't default to a value;
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// A value must be added before accessing the index
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intList.Add(1);
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Console.WriteLine("intList @ 0: " + intList[0]);
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// Others data structures to check out:
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//
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// Stack/Queue
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// Dictionary
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// Read-only Collections
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// Tuple (.Net 4+)
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///////////////////////////////////////
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// Operators
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///////////////////////////////////////
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Console.WriteLine("\n->Operators");
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int i1 = 1, i2 = 2; // Shorthand for multiple declarations
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// Arithmetic is straightforward
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Console.WriteLine("1+2 = " + (i1 + i2)); // => 3
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Console.WriteLine("2-1 = " + (i2 - i1)); // => 1
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Console.WriteLine("2*1 = " + (i2 * i1)); // => 2
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Console.WriteLine("1/2 = " + (i1 / i2)); // => 0 (0.5 truncated down)
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// Modulo
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Console.WriteLine("11%3 = " + (11 % 3)); // => 2
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// Comparison operators
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Console.WriteLine("3 == 2? " + (3 == 2)); // => false
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Console.WriteLine("3 != 2? " + (3 != 2)); // => true
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Console.WriteLine("3 > 2? " + (3 > 2)); // => true
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Console.WriteLine("3 < 2? " + (3 < 2)); // => false
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Console.WriteLine("2 <= 2? " + (2 <= 2)); // => true
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Console.WriteLine("2 >= 2? " + (2 >= 2)); // => true
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// Bitwise operators!
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/*
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~ Unary bitwise complement
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<< Signed left shift
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>> Signed right shift
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>>> Unsigned right shift
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& Bitwise AND
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^ Bitwise exclusive OR
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| Bitwise inclusive OR
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*/
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// Incrementations
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int i = 0;
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Console.WriteLine("\n->Inc/Dec-rementation");
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Console.WriteLine(i++); //i = 1. Post-Incrementation
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Console.WriteLine(++i); //i = 2. Pre-Incrementation
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Console.WriteLine(i--); //i = 1. Post-Decrementation
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Console.WriteLine(--i); //i = 0. Pre-Decrementation
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///////////////////////////////////////
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// Control Structures
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///////////////////////////////////////
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Console.WriteLine("\n->Control Structures");
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// If statements are c-like
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int j = 10;
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if (j == 10)
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{
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Console.WriteLine("I get printed");
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}
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else if (j > 10)
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{
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Console.WriteLine("I don't");
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}
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else
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{
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Console.WriteLine("I also don't");
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}
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// Ternary operators
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// A simple if/else can be written as follows
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// <condition> ? <true> : <false>
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string isTrue = (true) ? "True" : "False";
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Console.WriteLine("Ternary demo: " + isTrue);
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// While loop
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int fooWhile = 0;
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while (fooWhile < 100)
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{
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//Console.WriteLine(fooWhile);
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//Increment the counter
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//Iterated 99 times, fooWhile 0->99
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fooWhile++;
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}
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Console.WriteLine("fooWhile Value: " + fooWhile);
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// Do While Loop
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int fooDoWhile = 0;
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do
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{
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//Console.WriteLine(fooDoWhile);
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//Increment the counter
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//Iterated 99 times, fooDoWhile 0->99
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fooDoWhile++;
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} while (fooDoWhile < 100);
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Console.WriteLine("fooDoWhile Value: " + fooDoWhile);
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// For Loop
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int fooFor;
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//for loop structure => for(<start_statement>; <conditional>; <step>)
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for (fooFor = 0; fooFor < 10; fooFor++)
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{
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//Console.WriteLine(fooFor);
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//Iterated 10 times, fooFor 0->9
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}
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Console.WriteLine("fooFor Value: " + fooFor);
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// Switch Case
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// A switch works with the byte, short, char, and int data types.
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// It also works with enumerated types (discussed in Enum Types),
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// the String class, and a few special classes that wrap
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// primitive types: Character, Byte, Short, and Integer.
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int month = 3;
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string monthString;
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switch (month)
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{
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case 1:
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monthString = "January";
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break;
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case 2:
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monthString = "February";
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break;
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case 3:
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monthString = "March";
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break;
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default:
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monthString = "Some other month";
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break;
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}
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Console.WriteLine("Switch Case Result: " + monthString);
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///////////////////////////////////////
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// Converting Data Types And Typcasting
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///////////////////////////////////////
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// Converting data
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// Convert String To Integer
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// this will throw an Exception on failure
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int.Parse("123");//returns an integer version of "123"
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// try parse will default to type default on failure
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// in this case: 0
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int tryInt;
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int.TryParse("123", out tryInt);
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// Convert Integer To String
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// Convert class has a number of methods to facilitate conversions
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Convert.ToString(123);
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///////////////////////////////////////
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// Classes And Functions
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///////////////////////////////////////
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Console.WriteLine("\n->Classes & Functions");
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// (definition of the Bicycle class follows)
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// Use new to instantiate a class
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Bicycle trek = new Bicycle();
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// Call object methods
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trek.speedUp(3); // You should always use setter and getter methods
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trek.setCadence(100);
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// ToString is a convention to display the value of this Object.
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Console.WriteLine("trek info: " + trek.ToString());
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// Instantiate another new Bicycle
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Bicycle octo = new Bicycle(5, 10);
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Console.WriteLine("octo info: " + octo.ToString());
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// Instantiate a new Penny Farthing
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PennyFarthing funbike = new PennyFarthing(1, 10);
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Console.WriteLine("funbike info: " + funbike.ToString());
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Console.Read();
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} // End main method
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} // End LearnCSharp class
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// You can include other classes in a .cs file
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// Class Declaration Syntax:
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// <public/private/protected> class <class name>{
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// //data fields, constructors, functions all inside.
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// //functions are called as methods in Java.
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// }
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public class Bicycle
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{
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// Bicycle's Fields/Variables
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public int cadence; // Public: Can be accessed from anywhere
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private int _speed; // Private: Only accessible from within the class
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protected int gear; // Protected: Accessible from the class and subclasses
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internal int wheels; // Internal: Accessible from within the assembly
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string name; // default: Only accessible from within this class
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// readonly values are set at run time
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// they can only be assigned upon declaration or in a constructor
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readonly bool hasCardsInSpokes = false; // read-only private
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// Constructors are a way of creating classes
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// This is a default constructor
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public Bicycle()
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{
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gear = 1;
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cadence = 50;
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_speed = 5;
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name = "Bontrager";
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}
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// This is a specified constructor (it contains arguments)
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public Bicycle(int startCadence, int startSpeed, int startGear, string name, bool hasCardsInSpokes)
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{
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this.gear = startGear;
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this.cadence = startCadence;
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this._speed = startSpeed;
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this.name = name;
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this.hasCardsInSpokes = hasCardsInSpokes;
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}
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// Constructors can be chained
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public Bicycle(int startCadence, int startSpeed) :
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this(startCadence, startSpeed, 0, "big wheels", true)
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{
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}
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// Function Syntax:
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// <public/private/protected> <return type> <function name>(<args>)
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// classes can implement getters and setters for their fields
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// or they can implement properties
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// Method declaration syntax:
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// <scope> <return type> <method name>(<args>)
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public int getCadence()
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{
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return cadence;
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}
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// void methods require no return statement
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public void setCadence(int newValue)
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{
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cadence = newValue;
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}
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// virtual keyword indicates this method can be overridden
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public virtual void setGear(int newValue)
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{
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gear = newValue;
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}
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public void speedUp(int increment)
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{
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_speed += increment;
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}
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public void slowDown(int decrement)
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{
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_speed -= decrement;
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}
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// properties get/set values
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// when only data needs to be accessed, consider using properties.
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// properties may have either get or set, or both
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private bool _hasTassles; // private variable
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public bool hasTassles // public accessor
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{
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get { return _hasTassles; }
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set { _hasTassles = value; }
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}
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private int _frameSize;
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public int FrameSize
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{
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get { return _frameSize; }
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// you are able to specify access modifiers for either get or set
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// this means only Bicycle class can call set on Framesize
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private set { _frameSize = value; }
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}
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//Method to display the attribute values of this Object.
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public override string ToString()
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{
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return "gear: " + gear +
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" cadence: " + cadence +
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" speed: " + _speed +
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" name: " + name +
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" cards in spokes: " + (hasCardsInSpokes ? "yes" : "no") +
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"\n------------------------------\n"
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;
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}
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} // end class Bicycle
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// PennyFarthing is a subclass of Bicycle
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class PennyFarthing : Bicycle
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{
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// (Penny Farthings are those bicycles with the big front wheel.
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// They have no gears.)
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// calling parent constructor
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public PennyFarthing(int startCadence, int startSpeed) :
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base(startCadence, startSpeed, 0, "PennyFarthing", true)
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{
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}
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public override void setGear(int gear)
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{
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gear = 0;
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}
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}
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} // End Namespace
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```
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## Topics Not Covered
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* Enums, Flags
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* Attributes
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* Generics (T), Delegates, Func, Actions, lambda expressions
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* Exceptions, Interfaces, Abstraction
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* LINQ
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* ASP.NET (Web Forms/MVC/WebMatrix)
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* Winforms
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* Windows Presentation Foundation (WPF)
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## Further Reading
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* [DotNetPerls](http://www.dotnetperls.com)
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* [C# in Depth](http://manning.com/skeet2)
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* [Programming C#](http://shop.oreilly.com/product/0636920024064.do)
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* [LINQ](http://shop.oreilly.com/product/9780596519254.do)
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* [MSDN Library](http://msdn.microsoft.com/en-us/library/618ayhy6.aspx)
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* [ASP.NET MVC Tutorials](http://www.asp.net/mvc/tutorials)
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* [ASP.NET Web Matrix Tutorials](http://www.asp.net/web-pages/tutorials)
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* [ASP.NET Web Forms Tutorials](http://www.asp.net/web-forms/tutorials)
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* [Windows Forms Programming in C#](http://www.amazon.com/Windows-Forms-Programming-Chris-Sells/dp/0321116208)
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[C# Coding Conventions](http://msdn.microsoft.com/en-us/library/vstudio/ff926074.aspx)
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