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authorSuzane Sant Ana <tetestonaldo@gmail.com>2017-12-31 14:27:06 -0200
committerGitHub <noreply@github.com>2017-12-31 14:27:06 -0200
commit42f9329bb3a028d374d6397991ac48b44064741e (patch)
tree1e75e2b3e122aeb863e3ffa037f6f64c4027fbf8 /csharp.html.markdown
parente6b77595f2669d66ac7be43c6e6083cbff80a9a7 (diff)
parent70a36c9bd970b928adde06afb2bd69f6ba8e5d5c (diff)
Merge pull request #1 from adambard/master
update
Diffstat (limited to 'csharp.html.markdown')
-rw-r--r--csharp.html.markdown665
1 files changed, 582 insertions, 83 deletions
diff --git a/csharp.html.markdown b/csharp.html.markdown
index 47dd9683..f27adf18 100644
--- a/csharp.html.markdown
+++ b/csharp.html.markdown
@@ -5,6 +5,10 @@ contributors:
- ["Max Yankov", "https://github.com/golergka"]
- ["Melvyn Laïly", "http://x2a.yt"]
- ["Shaun McCarthy", "http://www.shaunmccarthy.com"]
+ - ["Wouter Van Schandevijl", "http://github.com/laoujin"]
+ - ["Jo Pearce", "http://github.com/jdpearce"]
+ - ["Chris Zimmerman", "https://github.com/chriszimmerman"]
+ - ["Shawn McGuire", "https://github.com/bigbash"]
filename: LearnCSharp.cs
---
@@ -18,29 +22,38 @@ C# is an elegant and type-safe object-oriented language that enables developers
Multi-line comments look like this
*/
/// <summary>
-/// This is an XML documentation comment
+/// This is an XML documentation comment which can be used to generate external
+/// documentation or provide context help within an IDE
/// </summary>
+/// <param name="firstParam">This is some parameter documentation for firstParam</param>
+/// <returns>Information on the returned value of a function</returns>
+//public void MethodOrClassOrOtherWithParsableHelp(string firstParam) {}
-// Specify namespaces application will be using
+// Specify the namespaces this source code will be using
+// The namespaces below are all part of the standard .NET Framework Class Library
using System;
using System.Collections.Generic;
-using System.Data.Entity;
using System.Dynamic;
using System.Linq;
-using System.Linq.Expressions;
using System.Net;
using System.Threading.Tasks;
using System.IO;
-// defines scope to organize code into "packages"
-namespace Learning
+// But this one is not:
+using System.Data.Entity;
+// In order to be able to use it, you need to add a dll reference
+// This can be done with the NuGet package manager: `Install-Package EntityFramework`
+
+// Namespaces define scope to organize code into "packages" or "modules"
+// Using this code from another source file: using Learning.CSharp;
+namespace Learning.CSharp
{
- // Each .cs file should at least contain a class with the same name as the file
- // you're allowed to do otherwise, but shouldn't for sanity.
+ // Each .cs file should at least contain a class with the same name as the file.
+ // You're allowed to do otherwise, but shouldn't for sanity.
public class LearnCSharp
{
// BASIC SYNTAX - skip to INTERESTING FEATURES if you have used Java or C++ before
- public static void Syntax()
+ public static void Syntax()
{
// Use Console.WriteLine to print lines
Console.WriteLine("Hello World");
@@ -119,13 +132,19 @@ namespace Learning
DateTime fooDate = DateTime.Now;
Console.WriteLine(fooDate.ToString("hh:mm, dd MMM yyyy"));
+ // Verbatim String
+ // You can use the @ symbol before a string literal to escape all characters in the string
+ string path = "C:\\Users\\User\\Desktop";
+ string verbatimPath = @"C:\Users\User\Desktop";
+ Console.WriteLine(path == verbatimPath); // => true
+
// You can split a string over two lines with the @ symbol. To escape " use ""
string bazString = @"Here's some stuff
on a new line! ""Wow!"", the masses cried";
// Use const or read-only to make a variable immutable
// const values are calculated at compile time
- const int HOURS_I_WORK_PER_WEEK = 9001;
+ const int HoursWorkPerWeek = 9001;
///////////////////////////////////////////////////
// Data Structures
@@ -151,7 +170,7 @@ on a new line! ""Wow!"", the masses cried";
// List<datatype> <var name> = new List<datatype>();
List<int> intList = new List<int>();
List<string> stringList = new List<string>();
- List<int> z = new List<int> { 9000, 1000, 1337 }; // intialize
+ List<int> z = new List<int> { 9000, 1000, 1337 }; // initialize
// The <> are for generics - Check out the cool stuff section
// Lists don't default to a value;
@@ -200,10 +219,10 @@ on a new line! ""Wow!"", the masses cried";
// Incrementations
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
+ Console.WriteLine(i++); //Prints "0", i = 1. Post-Incrementation
+ Console.WriteLine(++i); //Prints "2", i = 2. Pre-Incrementation
+ Console.WriteLine(i--); //Prints "2", i = 1. Post-Decrementation
+ Console.WriteLine(--i); //Prints "0", i = 0. Pre-Decrementation
///////////////////////////////////////
// Control Structures
@@ -228,7 +247,8 @@ on a new line! ""Wow!"", the masses cried";
// Ternary operators
// A simple if/else can be written as follows
// <condition> ? <true> : <false>
- string isTrue = (true) ? "True" : "False";
+ int toCompare = 17;
+ string isTrue = toCompare == 17 ? "True" : "False";
// While loop
int fooWhile = 0;
@@ -242,8 +262,15 @@ on a new line! ""Wow!"", the masses cried";
int fooDoWhile = 0;
do
{
- //Iterated 100 times, fooDoWhile 0->99
+ // Start iteration 100 times, fooDoWhile 0->99
+ if (false)
+ continue; // skip the current iteration
+
fooDoWhile++;
+
+ if (fooDoWhile == 50)
+ break; // breaks from the loop completely
+
} while (fooDoWhile < 100);
//for loop structure => for(<start_statement>; <conditional>; <step>)
@@ -301,7 +328,7 @@ on a new line! ""Wow!"", the masses cried";
// Converting data
// Convert String To Integer
- // this will throw an Exception on failure
+ // 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
@@ -315,6 +342,11 @@ on a new line! ""Wow!"", the masses cried";
Convert.ToString(123);
// or
tryInt.ToString();
+
+ // Casting
+ // Cast decimal 15 to a int
+ // and then implicitly cast to long
+ long x = (int) 15M;
}
///////////////////////////////////////
@@ -350,11 +382,11 @@ on a new line! ""Wow!"", the masses cried";
//
// INTERESTING FEATURES
//
-
+
// DEFAULT METHOD SIGNATURES
public // Visibility
- static // Allows for direct call on class without object
+ static // Allows for direct call on class without object
int // Return Type,
MethodSignatures(
int maxCount, // First variable, expects an int
@@ -362,21 +394,26 @@ on a new line! ""Wow!"", the masses cried";
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
- public static void MethodSignatures(string maxCount)
+ // A method that differs only in return type is not unique
+ public static void MethodSignatures(
+ ref int maxCount, // Pass by reference
+ out int count)
{
+ //the argument passed in as 'count' will hold the value of 15 outside of this function
+ 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,
+ IDictionary<TKey, TValue> dictionary,
+ TKey key,
TValue defaultItem)
{
TValue result;
@@ -385,7 +422,7 @@ on a new line! ""Wow!"", the masses cried";
return result;
}
- // You can narrow down the objects that are passed in
+ // 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
@@ -394,11 +431,51 @@ on a new line! ""Wow!"", the masses cried";
Console.WriteLine(item.ToString());
}
+ // YIELD
+ // Usage of the "yield" keyword indicates that the method it appears in is an Iterator
+ // (this means you can use it in a foreach loop)
+ public static IEnumerable<int> YieldCounter(int limit = 10)
+ {
+ for (var i = 0; i < limit; i++)
+ yield return i;
+ }
+
+ // which you would call like this :
+ public static void PrintYieldCounterToConsole()
+ {
+ foreach (var counter in YieldCounter())
+ Console.WriteLine(counter);
+ }
+
+ // you can use more than one "yield return" in a method
+ public static IEnumerable<int> ManyYieldCounter()
+ {
+ yield return 0;
+ yield return 1;
+ yield return 2;
+ yield return 3;
+ }
+
+ // you can also use "yield break" to stop the Iterator
+ // this method would only return half of the values from 0 to limit.
+ public static IEnumerable<int> YieldCounterWithBreak(int limit = 10)
+ {
+ for (var i = 0; i < limit; i++)
+ {
+ if (i > limit/2) yield break;
+ yield return i;
+ }
+ }
+
public static void OtherInterestingFeatures()
{
// OPTIONAL PARAMETERS
MethodSignatures(3, 1, 3, "Some", "Extra", "Strings");
- MethodSignatures(3, another: 3); // explicity set a parameter, skipping optional ones
+ MethodSignatures(3, another: 3); // explicitly 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;
@@ -415,19 +492,22 @@ on a new line! ""Wow!"", the masses cried";
// in case variable is null
int notNullable = nullable ?? 0; // 0
+ // ?. is an operator for null-propagation - a shorthand way of checking for null
+ nullable?.Print(); // Use the Print() extension method if nullable isn't null
+
// 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>() {
+ 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
+ // 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
@@ -435,41 +515,60 @@ on a new line! ""Wow!"", the masses cried";
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
+ // 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())
+
+ var words = new List<string> {"dog", "cat", "horse", "pony"};
+
+ Parallel.ForEach(words,
+ new ParallelOptions() { MaxDegreeOfParallelism = 4 },
+ word =>
{
- responses[website] = r.ContentType;
+ Console.WriteLine(word);
}
- });
+ );
- // This won't happen till after all requests have been completed
- foreach (var key in responses.Keys)
- Console.WriteLine("{0}:{1}", key, responses[key]);
+ //Running this will produce different outputs
+ //since each thread finishes at different times.
+ //Some example outputs are:
+ //cat dog horse pony
+ //dog horse pony cat
// DYNAMIC OBJECTS (great for working with other languages)
dynamic student = new ExpandoObject();
@@ -480,7 +579,7 @@ on a new line! ""Wow!"", the masses cried";
(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
+ // 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
@@ -500,10 +599,10 @@ on a new line! ""Wow!"", the masses cried";
Console.WriteLine(bikeSummary.Name);
// ASPARALLEL
- // And this is where things get wicked - combines linq and parallel operations
+ // And this is where things get wicked - combine 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
+ // 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
@@ -520,10 +619,10 @@ on a new line! ""Wow!"", the masses cried";
.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)
+ // Now the query runs, but opens a reader, so only populates as you iterate through
+ foreach (string bike in query)
Console.WriteLine(result);
-
+
}
@@ -534,13 +633,61 @@ on a new line! ""Wow!"", the masses cried";
public static class Extensions
{
- // EXTENSION FUNCTIONS
+ // EXTENSION METHODS
public static void Print(this object obj)
{
Console.WriteLine(obj.ToString());
}
}
+
+ // DELEGATES AND EVENTS
+ public class DelegateTest
+ {
+ public static int count = 0;
+ public static int Increment()
+ {
+ // increment count then return it
+ return ++count;
+ }
+
+ // A delegate is a reference to a method
+ // To reference the Increment method,
+ // first declare a delegate with the same signature
+ // ie. takes no arguments and returns an int
+ public delegate int IncrementDelegate();
+
+ // An event can also be used to trigger delegates
+ // Create an event with the delegate type
+ public static event IncrementDelegate MyEvent;
+
+ static void Main(string[] args)
+ {
+ // Refer to the Increment method by instantiating the delegate
+ // and passing the method itself in as an argument
+ IncrementDelegate inc = new IncrementDelegate(Increment);
+ Console.WriteLine(inc()); // => 1
+
+ // Delegates can be composed with the + operator
+ IncrementDelegate composedInc = inc;
+ composedInc += inc;
+ composedInc += inc;
+
+ // composedInc will run Increment 3 times
+ Console.WriteLine(composedInc()); // => 4
+
+
+ // Subscribe to the event with the delegate
+ MyEvent += new IncrementDelegate(Increment);
+ MyEvent += new IncrementDelegate(Increment);
+
+ // Trigger the event
+ // ie. run all delegates subscribed to this event
+ Console.WriteLine(MyEvent()); // => 6
+ }
+ }
+
+
// Class Declaration Syntax:
// <public/private/protected/internal> class <class name>{
// //data fields, constructors, functions all inside.
@@ -556,7 +703,7 @@ on a new line! ""Wow!"", the masses cried";
{
return _cadence;
}
- set // set - define a method to set a proprety
+ set // set - define a method to set a property
{
_cadence = value; // Value is the value passed in to the setter
}
@@ -575,9 +722,13 @@ on a new line! ""Wow!"", the masses cried";
private set; // You can set modifiers on the get/set methods
}
- int _speed; // Everything is private by default: Only accessible from within this class.
+ int _speed; // Everything is private by default: Only accessible from within this class.
// can also use keyword private
public string Name { get; set; }
+
+ // Properties also have a special syntax for when you want a readonly property
+ // that simply returns the result of an expression
+ public string LongName => Name + " " + _speed + " speed";
// 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).
@@ -595,10 +746,29 @@ on a new line! ""Wow!"", the masses cried";
public BikeBrand Brand; // After declaring an enum type, we can declare the field of this type
- // Static members belong to the type itself rather then specific object.
+ // Decorate an enum with the FlagsAttribute to indicate that multiple values can be switched on
+ // Any class derived from Attribute can be used to decorate types, methods, parameters etc
+ // Bitwise operators & and | can be used to perform and/or operations
+
+ [Flags]
+ 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 than specific object.
// You can access them without a reference to any object:
// Console.WriteLine("Bicycles created: " + Bicycle.bicyclesCreated);
- static public int BicyclesCreated = 0;
+ public static int BicyclesCreated { get; set; }
// readonly values are set at run time
// they can only be assigned upon declaration or in a constructor
@@ -606,7 +776,7 @@ on a new line! ""Wow!"", the masses cried";
// Constructors are a way of creating classes
// This is a default constructor
- public Bicycle()
+ 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
@@ -618,13 +788,13 @@ on a new line! ""Wow!"", the masses cried";
// This is a specified constructor (it contains arguments)
public Bicycle(int startCadence, int startSpeed, int startGear,
- string name, bool hasCardsInSpokes, BikeBrand brand)
+ string name, bool hasCardsInSpokes, BikeBrand brand)
: base() // calls base first
{
- Gear = startGear;
+ Gear = startGear;
Cadence = startCadence;
_speed = startSpeed;
- Name = name;
+ Name = name;
_hasCardsInSpokes = hasCardsInSpokes;
Brand = brand;
}
@@ -680,9 +850,9 @@ on a new line! ""Wow!"", the masses cried";
// 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
+ // could do bicycle[0] which returns "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" }
+ private string[] passengers = { "chris", "phil", "darren", "regina" };
public string this[int i]
{
@@ -691,7 +861,7 @@ on a new line! ""Wow!"", the masses cried";
}
set {
- return passengers[i] = value;
+ passengers[i] = value;
}
}
@@ -708,7 +878,7 @@ on a new line! ""Wow!"", the masses cried";
}
// Methods can also be static. It can be useful for helper methods
- public static bool DidWeCreateEnoughBycles()
+ public static bool DidWeCreateEnoughBicycles()
{
// Within a static method, we only can reference static class members
return BicyclesCreated > 9000;
@@ -737,10 +907,17 @@ on a new line! ""Wow!"", the masses cried";
}
set
{
- throw new ArgumentException("You can't change gears on a PennyFarthing");
+ 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 ";
@@ -760,7 +937,8 @@ on a new line! ""Wow!"", the masses cried";
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
+ // Classes can inherit only one other class, but can implement any amount of interfaces,
+ // however the base class name must be the first in the list and all interfaces follow
class MountainBike : Bicycle, IJumpable, IBreakable
{
int damage = 0;
@@ -780,11 +958,11 @@ on a new line! ""Wow!"", the masses cried";
}
/// <summary>
- /// Used to connect to DB for LinqToSql example.
+ /// 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 : DbSet
+ public class BikeRepository : DbContext
{
public BikeRepository()
: base()
@@ -793,18 +971,342 @@ on a new line! ""Wow!"", the masses cried";
public DbSet<Bicycle> Bikes { get; set; }
}
+
+ // Classes can be split across multiple .cs files
+ // A1.cs
+ public partial class A
+ {
+ public static void A1()
+ {
+ Console.WriteLine("Method A1 in class A");
+ }
+ }
+
+ // A2.cs
+ public partial class A
+ {
+ public static void A2()
+ {
+ Console.WriteLine("Method A2 in class A");
+ }
+ }
+
+ // Program using the partial class "A"
+ public class Program
+ {
+ static void Main()
+ {
+ A.A1();
+ A.A2();
+ }
+ }
+
+ // String interpolation by prefixing the string with $
+ // and wrapping the expression you want to interpolate with { braces }
+ // You can also combine both interpolated and verbatim strings with $@
+ public class Rectangle
+ {
+ public int Length { get; set; }
+ public int Width { get; set; }
+ }
+
+ class Program
+ {
+ static void Main(string[] args)
+ {
+ Rectangle rect = new Rectangle { Length = 5, Width = 3 };
+ Console.WriteLine($"The length is {rect.Length} and the width is {rect.Width}");
+
+ string username = "User";
+ Console.WriteLine($@"C:\Users\{username}\Desktop");
+ }
+ }
+
+ // New C# 6 features
+ class GlassBall : IJumpable, IBreakable
+ {
+ // Autoproperty initializers
+ public int Damage { get; private set; } = 0;
+
+ // Autoproperty initializers on getter-only properties
+ public string Name { get; } = "Glass ball";
+
+ // Getter-only autoproperty that is initialized in constructor
+ public string GenieName { get; }
+
+ public GlassBall(string genieName = null)
+ {
+ GenieName = genieName;
+ }
+
+ public void Jump(int meters)
+ {
+ if (meters < 0)
+ // New nameof() expression; compiler will check that the identifier exists
+ // nameof(x) == "x"
+ // Prevents e.g. parameter names changing but not updated in error messages
+ throw new ArgumentException("Cannot jump negative amount!", nameof(meters));
+
+ Damage += meters;
+ }
+
+ // Expression-bodied properties ...
+ public bool Broken
+ => Damage > 100;
+
+ // ... and methods
+ public override string ToString()
+ // Interpolated string
+ => $"{Name}. Damage taken: {Damage}";
+
+ public string SummonGenie()
+ // Null-conditional operators
+ // x?.y will return null immediately if x is null; y is not evaluated
+ => GenieName?.ToUpper();
+ }
+
+ static class MagicService
+ {
+ private static bool LogException(Exception ex)
+ {
+ /* log exception somewhere */
+ return false;
+ }
+
+ public static bool CastSpell(string spell)
+ {
+ try
+ {
+ // Pretend we call API here
+ throw new MagicServiceException("Spell failed", 42);
+
+ // Spell succeeded
+ return true;
+ }
+ // Only catch if Code is 42 i.e. spell failed
+ catch(MagicServiceException ex) when (ex.Code == 42)
+ {
+ // Spell failed
+ return false;
+ }
+ // Other exceptions, or MagicServiceException where Code is not 42
+ catch(Exception ex) when (LogException(ex))
+ {
+ // Execution never reaches this block
+ // The stack is not unwound
+ }
+ return false;
+ // Note that catching a MagicServiceException and rethrowing if Code
+ // is not 42 or 117 is different, as then the final catch-all block
+ // will not catch the rethrown exception
+ }
+ }
+
+ public class MagicServiceException : Exception
+ {
+ public int Code { get; }
+
+ public MagicServiceException(string message, int code) : base(message)
+ {
+ Code = code;
+ }
+ }
+
+ public static class PragmaWarning {
+ // Obsolete attribute
+ [Obsolete("Use NewMethod instead", false)]
+ public static void ObsoleteMethod()
+ {
+ /* obsolete code */
+ }
+
+ public static void NewMethod()
+ {
+ /* new code */
+ }
+
+ public static void Main()
+ {
+ ObsoleteMethod(); // CS0618: 'ObsoleteMethod is obsolete: Use NewMethod instead'
+#pragma warning disable CS0618
+ ObsoleteMethod(); // no warning
+#pragma warning restore CS0618
+ ObsoleteMethod(); // CS0618: 'ObsoleteMethod is obsolete: Use NewMethod instead'
+ }
+ }
} // End Namespace
+
+using System;
+// C# 6, static using
+using static System.Math;
+
+namespace Learning.More.CSharp
+{
+ class StaticUsing
+ {
+ static void Main()
+ {
+ // Without a static using statement..
+ Console.WriteLine("The square root of 4 is {}.", Math.Sqrt(4));
+ // With one
+ Console.WriteLine("The square root of 4 is {}.", Sqrt(4));
+ }
+ }
+}
+
+//New C# 7 Feature
+//Install Microsoft.Net.Compilers Latest from Nuget
+//Install System.ValueTuple Latest from Nuget
+using System;
+namespace Csharp7
+{
+ // TUPLES, DECONSTRUCTION AND DISCARDS
+ class TuplesTest
+ {
+ public (string, string) GetName()
+ {
+ // Fields in tuples are by default named Item1, Item2...
+ var names1 = ("Peter", "Parker");
+ Console.WriteLine(names1.Item2); // => Parker
+
+ // Fields can instead be explicitly named
+ // Type 1 Declaration
+ (string FirstName, string LastName) names2 = ("Peter", "Parker");
+
+ // Type 2 Declaration
+ var names3 = (First:"Peter", Last:"Parker");
+
+ Console.WriteLine(names2.FirstName); // => Peter
+ Console.WriteLine(names3.Last); // => Parker
+
+ return names3;
+ }
+
+ public string GetLastName() {
+ var fullName = GetName();
+
+ // Tuples can be deconstructed
+ (string firstName, string lastName) = fullName;
+
+ // Fields in a deconstructed tuple can be discarded by using _
+ var (_, last) = fullName;
+ return last;
+ }
+
+ // Any type can be deconstructed in the same way by
+ // specifying a Deconstruct method
+ public int randomNumber = 4;
+ public int anotherRandomNumber = 10;
+
+ public void Deconstruct(out int randomNumber, out int anotherRandomNumber)
+ {
+ randomNumber = this.randomNumber;
+ anotherRandomNumber = this.anotherRandomNumber;
+ }
+
+ static void Main(string[] args)
+ {
+ var tt = new TuplesTest();
+ (int num1, int num2) = tt;
+ Console.WriteLine($"num1: {num1}, num2: {num2}"); // => num1: 4, num2: 10
+
+ Console.WriteLine(tt.GetLastName());
+ }
+ }
+
+ // PATTERN MATCHING
+ class PatternMatchingTest
+ {
+ public static (string, int)? CreateLogMessage(object data)
+ {
+ switch(data)
+ {
+ // Additional filtering using when
+ case System.Net.Http.HttpRequestException h when h.Message.Contains("404"):
+ return (h.Message, 404);
+ case System.Net.Http.HttpRequestException h when h.Message.Contains("400"):
+ return (h.Message, 400);
+ case Exception e:
+ return (e.Message, 500);
+ case string s:
+ return (s, s.Contains("Error") ? 500 : 200);
+ case null:
+ return null;
+ default:
+ return (data.ToString(), 500);
+ }
+ }
+ }
+
+ // REFERENCE LOCALS
+ // Allow you to return a reference to an object instead of just its value
+ class RefLocalsTest
+ {
+ // note ref in return
+ public static ref string FindItem(string[] arr, string el)
+ {
+ for(int i=0; i<arr.Length; i++)
+ {
+ if(arr[i] == el) {
+ // return the reference
+ return ref arr[i];
+ }
+ }
+ throw new Exception("Item not found");
+ }
+
+ public static void SomeMethod()
+ {
+ string[] arr = {"this", "is", "an", "array"};
+
+ // note refs everywhere
+ ref string item = ref FindItem(arr, "array");
+ item = "apple";
+ Console.WriteLine(arr[3]); // => apple
+ }
+ }
+
+ // LOCAL FUNCTIONS
+ class LocalFunctionTest
+ {
+ private static int _id = 0;
+ public int id;
+ public LocalFunctionTest()
+ {
+ id = generateId();
+
+ // This local function can only be accessed in this scope
+ int generateId()
+ {
+ return _id++;
+ }
+ }
+
+ public static void AnotherMethod()
+ {
+ var lf1 = new LocalFunctionTest();
+ var lf2 = new LocalFunctionTest();
+ Console.WriteLine($"{lf1.id}, {lf2.id}"); // => 0, 1
+
+ int id = generateId();
+ // error CS0103: The name 'generateId' does not exist in the current context
+ }
+ }
+}
+
```
## Topics Not Covered
- * Flags
* Attributes
- * Static properties
- * Exceptions, Abstraction
- * ASP.NET (Web Forms/MVC/WebMatrix)
- * Winforms
- * Windows Presentation Foundation (WPF)
+ * async/await
+ * 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
@@ -817,7 +1319,4 @@ on a new line! ""Wow!"", the masses cried";
* [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)
+ * [C# Coding Conventions](http://msdn.microsoft.com/en-us/library/vstudio/ff926074.aspx)