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diff --git a/pt-br/csharp.html.markdown b/pt-br/csharp.html.markdown new file mode 100644 index 00000000..547f4817 --- /dev/null +++ b/pt-br/csharp.html.markdown @@ -0,0 +1,896 @@ +--- +language: c# +filename: csharp-pt.cs +contributors: + - ["Robson Alves", "http://robsonalves.net/"] +lang: pt-br +--- + +C# é uma linguagem elegante e altamente tipado orientada a objetos que permite aos desenvolvedores criarem uma variedade de aplicações seguras e robustas que são executadas no .NET Framework. + +[Read more here.](http://msdn.microsoft.com/pt-br/library/vstudio/z1zx9t92.aspx) + +```c# +// Comentário de linha única começa com // +/* +Múltipas linhas é desta forma +*/ +/// <summary> +/// Esta é uma documentação comentário XML que pode ser usado para gerar externo +/// documentação ou fornecer ajuda de contexto dentro de um IDE +/// </summary> +//public void MethodOrClassOrOtherWithParsableHelp() {} + +// Especificar qual namespace seu código irá usar +// Os namespaces a seguir são padrões do .NET Framework Class Library +using System; +using System.Collections.Generic; +using System.Dynamic; +using System.Linq; +using System.Net; +using System.Threading.Tasks; +using System.IO; + +// Mas este aqui não é : +using System.Data.Entity; +// Para que consiga utiliza-lo, você precisa adicionar novas referências +// Isso pode ser feito com o gerenciador de pacotes NuGet : `Install-Package EntityFramework` + +// Namespaces são escopos definidos para organizar o códgo em "pacotes" or "módulos" +// Usando este código a partir de outra arquivo de origem: using Learning.CSharp; +namespace Learning.CSharp +{ + // Cada .cs deve conter uma classe com o mesmo nome do arquivo + // você está autorizado a contrariar isto, mas evite por sua sanidade. + public class AprenderCsharp + { + // Sintaxe Básica - Pule para as CARACTERÍSTICAS INTERESSANTES se você ja usou Java ou C++ antes. + public static void Syntax() + { + // Use Console.WriteLine para apresentar uma linha + Console.WriteLine("Hello World"); + Console.WriteLine( + "Integer: " + 10 + + " Double: " + 3.14 + + " Boolean: " + true); + + // Para apresentar sem incluir uma nova linha, use Console.Write + Console.Write("Hello "); + Console.Write("World"); + + /////////////////////////////////////////////////// + // Tpos e Variáveis + // + // Declare uma variável usando <tipo> <nome> + /////////////////////////////////////////////////// + + // Sbyte - Signed 8-bit integer + // (-128 <= sbyte <= 127) + sbyte fooSbyte = 100; + + // Byte - Unsigned 8-bit integer + // (0 <= byte <= 255) + byte fooByte = 100; + + // Short - 16-bit integer + // Signed - (-32,768 <= short <= 32,767) + // Unsigned - (0 <= ushort <= 65,535) + short fooShort = 10000; + ushort fooUshort = 10000; + + // Integer - 32-bit integer + int fooInt = 1; // (-2,147,483,648 <= int <= 2,147,483,647) + uint fooUint = 1; // (0 <= uint <= 4,294,967,295) + + // Long - 64-bit integer + long fooLong = 100000L; // (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807) + ulong fooUlong = 100000L; // (0 <= ulong <= 18,446,744,073,709,551,615) + // Numbers default to being int or uint depending on size. + // L is used to denote that this variable value is of type long or ulong + + // Double - Double-precision 64-bit IEEE 754 Floating Point + double fooDouble = 123.4; // Precision: 15-16 digits + + // Float - Single-precision 32-bit IEEE 754 Floating Point + float fooFloat = 234.5f; // Precision: 7 digits + // f is used to denote that this variable value is of type float + + // Decimal - a 128-bits data type, with more precision than other floating-point types, + // suited for financial and monetary calculations + decimal fooDecimal = 150.3m; + + // Boolean - true & false + bool fooBoolean = true; // or false + + // Char - A single 16-bit Unicode character + char fooChar = 'A'; + + // Strings - ao contrário dos anteriores tipos base, que são todos os tipos de valor, + // Uma string é um tipo de referência. Ou seja, você pode configurá-lo como nulo + string fooString = "\"escape\" quotes and add \n (new lines) and \t (tabs)"; + Console.WriteLine(fooString); + + // Você pode acessar todos os caracteres de string com um indexador: + char charFromString = fooString[1]; // => 'e' + // Strings são imutáveis: você não pode fazer fooString[1] = 'X'; + + // Compare strings com sua atual cultura, ignorando maiúsculas e minúsculas + string.Compare(fooString, "x", StringComparison.CurrentCultureIgnoreCase); + + // Formatando, baseado no sprintf + string fooFs = string.Format("Check Check, {0} {1}, {0} {1:0.0}", 1, 2); + + // Datas e formatações + DateTime fooDate = DateTime.Now; + Console.WriteLine(fooDate.ToString("hh:mm, dd MMM yyyy")); + + // Você pode juntar um string em mais de duas linhas com o símbolo @. Para escapar do " use "" + string bazString = @"Here's some stuff +on a new line! ""Wow!"", the masses cried"; + + // Use const ou read-only para fazer uma variável imutável + // os valores da const são calculados durante o tempo de compilação + const int HoursWorkPerWeek = 9001; + + /////////////////////////////////////////////////// + // Estrutura de Dados + /////////////////////////////////////////////////// + + // Matrizes - zero indexado + // O tamanho do array pode ser decidido ainda na declaração + // O formato para declarar uma matriz é o seguinte: + // <tipodado>[] <var nome> = new <tipodado>[<array tamanho>]; + int[] intArray = new int[10]; + + // Outra forma de declarar & inicializar uma matriz + int[] y = { 9000, 1000, 1337 }; + + // Indexando uma matriz - Acessando um elemento + Console.WriteLine("intArray @ 0: " + intArray[0]); + // Matriz são alteráveis + intArray[1] = 1; + + // Listas + // Listas são usadas frequentemente tanto quanto matriz por serem mais flexiveis + // O formato de declarar uma lista é o seguinte: + // List<tipodado> <var nome> = new List<tipodado>(); + List<int> intList = new List<int>(); + List<string> stringList = new List<string>(); + List<int> z = new List<int> { 9000, 1000, 1337 }; // inicializar + // O <> são para genéricos - Confira está interessante seção do material + + // Lista não possuem valores padrão. + // Um valor deve ser adicionado antes e depois acessado pelo indexador + intList.Add(1); + Console.WriteLine("intList @ 0: " + intList[0]); + + // Outras estruturas de dados para conferir: + // Pilha/Fila + // Dicionário (uma implementação de map de hash) + // HashSet + // Read-only Coleção + // Tuple (.Net 4+) + + /////////////////////////////////////// + // Operadores + /////////////////////////////////////// + Console.WriteLine("\n->Operators"); + + int i1 = 1, i2 = 2; // Forma curta para declarar diversas variáveis + + // Aritmética é clara + Console.WriteLine(i1 + i2 - i1 * 3 / 7); // => 3 + + // Modulo + Console.WriteLine("11%3 = " + (11 % 3)); // => 2 + + // Comparações de operadores + Console.WriteLine("3 == 2? " + (3 == 2)); // => falso + Console.WriteLine("3 != 2? " + (3 != 2)); // => verdadeiro + Console.WriteLine("3 > 2? " + (3 > 2)); // => verdadeiro + Console.WriteLine("3 < 2? " + (3 < 2)); // => falso + Console.WriteLine("2 <= 2? " + (2 <= 2)); // => verdadeiro + Console.WriteLine("2 >= 2? " + (2 >= 2)); // => verdadeiro + + // Operadores bit a bit (bitwise) + /* + ~ Unário bitwise complemento + << Signed left shift + >> Signed right shift + & Bitwise AND + ^ Bitwise exclusivo OR + | Bitwise inclusivo OR + */ + + // Incrementações + int i = 0; + Console.WriteLine("\n->Inc/Dec-rementation"); + Console.WriteLine(i++); //i = 1. Post-Incrementation + Console.WriteLine(++i); //i = 2. Pre-Incrementation + Console.WriteLine(i--); //i = 1. Post-Decrementation + Console.WriteLine(--i); //i = 0. Pre-Decrementation + + /////////////////////////////////////// + // Estrutura de Controle + /////////////////////////////////////// + Console.WriteLine("\n->Control Structures"); + + // Declaração if é como a linguagem C + int j = 10; + if (j == 10) + { + Console.WriteLine("I get printed"); + } + else if (j > 10) + { + Console.WriteLine("I don't"); + } + else + { + Console.WriteLine("I also don't"); + } + + // Operador Ternário + // Um simples if/else pode ser escrito da seguinte forma + // <condição> ? <verdadeiro> : <falso> + int toCompare = 17; + string isTrue = toCompare == 17 ? "True" : "False"; + + // While loop + int fooWhile = 0; + while (fooWhile < 100) + { + //Iterated 100 times, fooWhile 0->99 + fooWhile++; + } + + // Do While Loop + int fooDoWhile = 0; + do + { + // Inicia a interação 100 vezes, fooDoWhile 0->99 + if (false) + continue; // pule a intereção atual para apróxima + + fooDoWhile++; + + if (fooDoWhile == 50) + break; // Interrompe o laço inteiro + + } while (fooDoWhile < 100); + + //estrutura de loop for => for(<declaração para começar>; <condicional>; <passos>) + for (int fooFor = 0; fooFor < 10; fooFor++) + { + //Iterado 10 vezes, fooFor 0->9 + } + + // For Each Loop + // Estrutura do foreach => foreach(<Tipo Iterador> <Nome do Iterador> in <enumerable>) + // O laço foreach percorre sobre qualquer objeto que implementa IEnumerable ou IEnumerable<T> + // Toda a coleção de tipos (Array, List, Dictionary...) no .Net framework + // implementa uma ou mais destas interfaces. + // (O ToCharArray() pode ser removido, por que uma string também implementa IEnumerable) + foreach (char character in "Hello World".ToCharArray()) + { + //Iterated over all the characters in the string + } + + // Switch Case + // Um switch funciona com os tipos de dados byte, short, char, e int. + // Isto também funcional com tipos enumeradors (discutidos em Tipos Enum), + // A classe String, and a few special classes that wrap + // tipos primitívos: Character, Byte, Short, and Integer. + int month = 3; + string monthString; + switch (month) + { + case 1: + monthString = "January"; + break; + case 2: + monthString = "February"; + break; + case 3: + monthString = "March"; + break; + // You can assign more than one case to an action + // But you can't add an action without a break before another case + // (if you want to do this, you would have to explicitly add a goto case x + case 6: + case 7: + case 8: + monthString = "Summer time!!"; + break; + default: + monthString = "Some other month"; + break; + } + + /////////////////////////////////////// + // Converting Data Types And Typecasting + /////////////////////////////////////// + + // Converting data + + // Convert String To Integer + // this will throw a FormatException on failure + int.Parse("123");//returns an integer version of "123" + + // try parse will default to type default on failure + // in this case: 0 + int tryInt; + if (int.TryParse("123", out tryInt)) // Function is boolean + Console.WriteLine(tryInt); // 123 + + // Convert Integer To String + // Convert class has a number of methods to facilitate conversions + Convert.ToString(123); + // or + tryInt.ToString(); + + // Casting + // Cast decimal 15 to a int + // and then implicitly cast to long + long x = (int) 15M; + } + + /////////////////////////////////////// + // CLASSES - see definitions at end of file + /////////////////////////////////////// + public static void Classes() + { + // See Declaration of objects at end of file + + // Use new to instantiate a class + Bicycle trek = new Bicycle(); + + // Call object methods + trek.SpeedUp(3); // You should always use setter and getter methods + trek.Cadence = 100; + + // ToString is a convention to display the value of this Object. + Console.WriteLine("trek info: " + trek.Info()); + + // Instantiate a new Penny Farthing + PennyFarthing funbike = new PennyFarthing(1, 10); + Console.WriteLine("funbike info: " + funbike.Info()); + + Console.Read(); + } // End main method + + // CONSOLE ENTRY A console application must have a main method as an entry point + public static void Main(string[] args) + { + OtherInterestingFeatures(); + } + + // + // INTERESTING FEATURES + // + + // DEFAULT METHOD SIGNATURES + + public // Visibility + static // Allows for direct call on class without object + int // Return Type, + MethodSignatures( + int maxCount, // First variable, expects an int + int count = 0, // will default the value to 0 if not passed in + int another = 3, + params string[] otherParams // captures all other parameters passed to method + ) + { + return -1; + } + + // Methods can have the same name, as long as the signature is unique + // A method that differs only in return type is not unique + public static void MethodSignatures( + ref int maxCount, // Pass by reference + out int count) + { + count = 15; // out param must be assigned before control leaves the method + } + + // GENERICS + // The classes for TKey and TValue is specified by the user calling this function. + // This method emulates the SetDefault of Python + public static TValue SetDefault<TKey, TValue>( + IDictionary<TKey, TValue> dictionary, + TKey key, + TValue defaultItem) + { + TValue result; + if (!dictionary.TryGetValue(key, out result)) + return dictionary[key] = defaultItem; + return result; + } + + // You can narrow down the objects that are passed in + public static void IterateAndPrint<T>(T toPrint) where T: IEnumerable<int> + { + // We can iterate, since T is a IEnumerable + foreach (var item in toPrint) + // Item is an int + Console.WriteLine(item.ToString()); + } + + public static void OtherInterestingFeatures() + { + // OPTIONAL PARAMETERS + MethodSignatures(3, 1, 3, "Some", "Extra", "Strings"); + MethodSignatures(3, another: 3); // explicity set a parameter, skipping optional ones + + // BY REF AND OUT PARAMETERS + int maxCount = 0, count; // ref params must have value + MethodSignatures(ref maxCount, out count); + + // EXTENSION METHODS + int i = 3; + i.Print(); // Defined below + + // NULLABLE TYPES - great for database interaction / return values + // any value type (i.e. not a class) can be made nullable by suffixing a ? + // <type>? <var name> = <value> + int? nullable = null; // short hand for Nullable<int> + Console.WriteLine("Nullable variable: " + nullable); + bool hasValue = nullable.HasValue; // true if not null + + // ?? is syntactic sugar for specifying default value (coalesce) + // in case variable is null + int notNullable = nullable ?? 0; // 0 + + // IMPLICITLY TYPED VARIABLES - you can let the compiler work out what the type is: + var magic = "magic is a string, at compile time, so you still get type safety"; + // magic = 9; will not work as magic is a string, not an int + + // GENERICS + // + var phonebook = new Dictionary<string, string>() { + {"Sarah", "212 555 5555"} // Add some entries to the phone book + }; + + // Calling SETDEFAULT defined as a generic above + Console.WriteLine(SetDefault<string,string>(phonebook, "Shaun", "No Phone")); // No Phone + // nb, you don't need to specify the TKey and TValue since they can be + // derived implicitly + Console.WriteLine(SetDefault(phonebook, "Sarah", "No Phone")); // 212 555 5555 + + // LAMBDA EXPRESSIONS - allow you to write code in line + Func<int, int> square = (x) => x * x; // Last T item is the return value + Console.WriteLine(square(3)); // 9 + + // ERROR HANDLING - coping with an uncertain world + try + { + var funBike = PennyFarthing.CreateWithGears(6); + + // will no longer execute because CreateWithGears throws an exception + string some = ""; + if (true) some = null; + some.ToLower(); // throws a NullReferenceException + } + catch (NotSupportedException) + { + Console.WriteLine("Not so much fun now!"); + } + catch (Exception ex) // catch all other exceptions + { + throw new ApplicationException("It hit the fan", ex); + // throw; // A rethrow that preserves the callstack + } + // catch { } // catch-all without capturing the Exception + finally + { + // executes after try or catch + } + + // DISPOSABLE RESOURCES MANAGEMENT - let you handle unmanaged resources easily. + // Most of objects that access unmanaged resources (file handle, device contexts, etc.) + // implement the IDisposable interface. The using statement takes care of + // cleaning those IDisposable objects for you. + using (StreamWriter writer = new StreamWriter("log.txt")) + { + writer.WriteLine("Nothing suspicious here"); + // At the end of scope, resources will be released. + // Even if an exception is thrown. + } + + // PARALLEL FRAMEWORK + // http://blogs.msdn.com/b/csharpfaq/archive/2010/06/01/parallel-programming-in-net-framework-4-getting-started.aspx + var websites = new string[] { + "http://www.google.com", "http://www.reddit.com", + "http://www.shaunmccarthy.com" + }; + var responses = new Dictionary<string, string>(); + + // Will spin up separate threads for each request, and join on them + // before going to the next step! + Parallel.ForEach(websites, + new ParallelOptions() {MaxDegreeOfParallelism = 3}, // max of 3 threads + website => + { + // Do something that takes a long time on the file + using (var r = WebRequest.Create(new Uri(website)).GetResponse()) + { + responses[website] = r.ContentType; + } + }); + + // This won't happen till after all requests have been completed + foreach (var key in responses.Keys) + Console.WriteLine("{0}:{1}", key, responses[key]); + + // DYNAMIC OBJECTS (great for working with other languages) + dynamic student = new ExpandoObject(); + student.FirstName = "First Name"; // No need to define class first! + + // You can even add methods (returns a string, and takes in a string) + student.Introduce = new Func<string, string>( + (introduceTo) => string.Format("Hey {0}, this is {1}", student.FirstName, introduceTo)); + Console.WriteLine(student.Introduce("Beth")); + + // IQUERYABLE<T> - almost all collections implement this, which gives you a lot of + // very useful Map / Filter / Reduce style methods + var bikes = new List<Bicycle>(); + bikes.Sort(); // Sorts the array + bikes.Sort((b1, b2) => b1.Wheels.CompareTo(b2.Wheels)); // Sorts based on wheels + var result = bikes + .Where(b => b.Wheels > 3) // Filters - chainable (returns IQueryable of previous type) + .Where(b => b.IsBroken && b.HasTassles) + .Select(b => b.ToString()); // Map - we only this selects, so result is a IQueryable<string> + + var sum = bikes.Sum(b => b.Wheels); // Reduce - sums all the wheels in the collection + + // Create a list of IMPLICIT objects based on some parameters of the bike + var bikeSummaries = bikes.Select(b=>new { Name = b.Name, IsAwesome = !b.IsBroken && b.HasTassles }); + // Hard to show here, but you get type ahead completion since the compiler can implicitly work + // out the types above! + foreach (var bikeSummary in bikeSummaries.Where(b => b.IsAwesome)) + Console.WriteLine(bikeSummary.Name); + + // ASPARALLEL + // And this is where things get wicked - combines linq and parallel operations + var threeWheelers = bikes.AsParallel().Where(b => b.Wheels == 3).Select(b => b.Name); + // this will happen in parallel! Threads will automagically be spun up and the + // results divvied amongst them! Amazing for large datasets when you have lots of + // cores + + // LINQ - maps a store to IQueryable<T> objects, with delayed execution + // e.g. LinqToSql - maps to a database, LinqToXml maps to an xml document + var db = new BikeRepository(); + + // execution is delayed, which is great when querying a database + var filter = db.Bikes.Where(b => b.HasTassles); // no query run + if (42 > 6) // You can keep adding filters, even conditionally - great for "advanced search" functionality + filter = filter.Where(b => b.IsBroken); // no query run + + var query = filter + .OrderBy(b => b.Wheels) + .ThenBy(b => b.Name) + .Select(b => b.Name); // still no query run + + // Now the query runs, but opens a reader, so only populates are you iterate through + foreach (string bike in query) + Console.WriteLine(result); + + + + } + + } // End LearnCSharp class + + // You can include other classes in a .cs file + + public static class Extensions + { + // EXTENSION FUNCTIONS + public static void Print(this object obj) + { + Console.WriteLine(obj.ToString()); + } + } + + // Class Declaration Syntax: + // <public/private/protected/internal> class <class name>{ + // //data fields, constructors, functions all inside. + // //functions are called as methods in Java. + // } + + public class Bicycle + { + // Bicycle's Fields/Variables + public int Cadence // Public: Can be accessed from anywhere + { + get // get - define a method to retrieve the property + { + return _cadence; + } + set // set - define a method to set a proprety + { + _cadence = value; // Value is the value passed in to the setter + } + } + private int _cadence; + + protected virtual int Gear // Protected: Accessible from the class and subclasses + { + get; // creates an auto property so you don't need a member field + set; + } + + internal int Wheels // Internal: Accessible from within the assembly + { + get; + private set; // You can set modifiers on the get/set methods + } + + int _speed; // Everything is private by default: Only accessible from within this class. + // can also use keyword private + public string Name { get; set; } + + // Enum is a value type that consists of a set of named constants + // It is really just mapping a name to a value (an int, unless specified otherwise). + // The approved types for an enum are byte, sbyte, short, ushort, int, uint, long, or ulong. + // An enum can't contain the same value twice. + public enum BikeBrand + { + AIST, + BMC, + Electra = 42, //you can explicitly set a value to a name + Gitane // 43 + } + // We defined this type inside a Bicycle class, so it is a nested type + // Code outside of this class should reference this type as Bicycle.Brand + + public BikeBrand Brand; // After declaring an enum type, we can declare the field of this type + + // Decorate an enum with the FlagsAttribute to indicate that multiple values can be switched on + [Flags] // Any class derived from Attribute can be used to decorate types, methods, parameters etc + public enum BikeAccessories + { + None = 0, + Bell = 1, + MudGuards = 2, // need to set the values manually! + Racks = 4, + Lights = 8, + FullPackage = Bell | MudGuards | Racks | Lights + } + + // Usage: aBike.Accessories.HasFlag(Bicycle.BikeAccessories.Bell) + // Before .NET 4: (aBike.Accessories & Bicycle.BikeAccessories.Bell) == Bicycle.BikeAccessories.Bell + public BikeAccessories Accessories { get; set; } + + // Static members belong to the type itself rather then specific object. + // You can access them without a reference to any object: + // Console.WriteLine("Bicycles created: " + Bicycle.bicyclesCreated); + public static int BicyclesCreated { get; set; } + + // readonly values are set at run time + // they can only be assigned upon declaration or in a constructor + readonly bool _hasCardsInSpokes = false; // read-only private + + // Constructors are a way of creating classes + // This is a default constructor + public Bicycle() + { + this.Gear = 1; // you can access members of the object with the keyword this + Cadence = 50; // but you don't always need it + _speed = 5; + Name = "Bontrager"; + Brand = BikeBrand.AIST; + BicyclesCreated++; + } + + // This is a specified constructor (it contains arguments) + public Bicycle(int startCadence, int startSpeed, int startGear, + string name, bool hasCardsInSpokes, BikeBrand brand) + : base() // calls base first + { + Gear = startGear; + Cadence = startCadence; + _speed = startSpeed; + Name = name; + _hasCardsInSpokes = hasCardsInSpokes; + Brand = brand; + } + + // Constructors can be chained + public Bicycle(int startCadence, int startSpeed, BikeBrand brand) : + this(startCadence, startSpeed, 0, "big wheels", true, brand) + { + } + + // Function Syntax: + // <public/private/protected> <return type> <function name>(<args>) + + // classes can implement getters and setters for their fields + // or they can implement properties (this is the preferred way in C#) + + // Method parameters can have default values. + // In this case, methods can be called with these parameters omitted + public void SpeedUp(int increment = 1) + { + _speed += increment; + } + + public void SlowDown(int decrement = 1) + { + _speed -= decrement; + } + + // properties get/set values + // when only data needs to be accessed, consider using properties. + // properties may have either get or set, or both + private bool _hasTassles; // private variable + public bool HasTassles // public accessor + { + get { return _hasTassles; } + set { _hasTassles = value; } + } + + // You can also define an automatic property in one line + // this syntax will create a backing field automatically. + // You can set an access modifier on either the getter or the setter (or both) + // to restrict its access: + public bool IsBroken { get; private set; } + + // Properties can be auto-implemented + public int FrameSize + { + get; + // you are able to specify access modifiers for either get or set + // this means only Bicycle class can call set on Framesize + private set; + } + + // It's also possible to define custom Indexers on objects. + // All though this is not entirely useful in this example, you + // could do bicycle[0] which yields "chris" to get the first passenger or + // bicycle[1] = "lisa" to set the passenger. (of this apparent quattrocycle) + private string[] passengers = { "chris", "phil", "darren", "regina" }; + + public string this[int i] + { + get { + return passengers[i]; + } + + set { + return passengers[i] = value; + } + } + + //Method to display the attribute values of this Object. + public virtual string Info() + { + return "Gear: " + Gear + + " Cadence: " + Cadence + + " Speed: " + _speed + + " Name: " + Name + + " Cards in Spokes: " + (_hasCardsInSpokes ? "yes" : "no") + + "\n------------------------------\n" + ; + } + + // Methods can also be static. It can be useful for helper methods + public static bool DidWeCreateEnoughBycles() + { + // Within a static method, we only can reference static class members + return BicyclesCreated > 9000; + } // If your class only needs static members, consider marking the class itself as static. + + + } // end class Bicycle + + // PennyFarthing is a subclass of Bicycle + class PennyFarthing : Bicycle + { + // (Penny Farthings are those bicycles with the big front wheel. + // They have no gears.) + + // calling parent constructor + public PennyFarthing(int startCadence, int startSpeed) : + base(startCadence, startSpeed, 0, "PennyFarthing", true, BikeBrand.Electra) + { + } + + protected override int Gear + { + get + { + return 0; + } + set + { + throw new InvalidOperationException("You can't change gears on a PennyFarthing"); + } + } + + public static PennyFarthing CreateWithGears(int gears) + { + var penny = new PennyFarthing(1, 1); + penny.Gear = gears; // Oops, can't do this! + return penny; + } + + public override string Info() + { + string result = "PennyFarthing bicycle "; + result += base.ToString(); // Calling the base version of the method + return result; + } + } + + // Interfaces only contain signatures of the members, without the implementation. + interface IJumpable + { + void Jump(int meters); // all interface members are implicitly public + } + + interface IBreakable + { + bool Broken { get; } // interfaces can contain properties as well as methods & events + } + + // Class can inherit only one other class, but can implement any amount of interfaces + class MountainBike : Bicycle, IJumpable, IBreakable + { + int damage = 0; + + public void Jump(int meters) + { + damage += meters; + } + + public bool Broken + { + get + { + return damage > 100; + } + } + } + + /// <summary> + /// Used to connect to DB for LinqToSql example. + /// EntityFramework Code First is awesome (similar to Ruby's ActiveRecord, but bidirectional) + /// http://msdn.microsoft.com/en-us/data/jj193542.aspx + /// </summary> + public class BikeRepository : DbContext + { + public BikeRepository() + : base() + { + } + + public DbSet<Bicycle> Bikes { get; set; } + } +} // End Namespace +``` + +## Topics Not Covered + + * Attributes + * async/await, yield, pragma directives + * Web Development + * ASP.NET MVC & WebApi (new) + * ASP.NET Web Forms (old) + * WebMatrix (tool) + * Desktop Development + * Windows Presentation Foundation (WPF) (new) + * Winforms (old) + +## Further Reading + + * [DotNetPerls](http://www.dotnetperls.com) + * [C# in Depth](http://manning.com/skeet2) + * [Programming C#](http://shop.oreilly.com/product/0636920024064.do) + * [LINQ](http://shop.oreilly.com/product/9780596519254.do) + * [MSDN Library](http://msdn.microsoft.com/en-us/library/618ayhy6.aspx) + * [ASP.NET MVC Tutorials](http://www.asp.net/mvc/tutorials) + * [ASP.NET Web Matrix Tutorials](http://www.asp.net/web-pages/tutorials) + * [ASP.NET Web Forms Tutorials](http://www.asp.net/web-forms/tutorials) + * [Windows Forms Programming in C#](http://www.amazon.com/Windows-Forms-Programming-Chris-Sells/dp/0321116208) + * [C# Coding Conventions](http://msdn.microsoft.com/en-us/library/vstudio/ff926074.aspx) |