DEV321 Visual C# 2005: Language Enhancements 1/14/2019 1:33 AM DEV321 Visual C# 2005: Language Enhancements Anders Hejlsberg Distinguished Engineer Microsoft Corporation © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

C# Language Enhancements 1/14/2019 1:33 AM C# Language Enhancements Generics Anonymous methods Nullable types Iterators Partial types and many more… 100% backwards compatible © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Generics public class List { private object[] elements; 1/14/2019 1:33 AM Generics public class List { private object[] elements; private int count; public void Add(object element) { if (count == elements.Length) Resize(count * 2); elements[count++] = element; } public object this[int index] { get { return elements[index]; } set { elements[index] = value; } public int Count { get { return count; } public class List<T> { private T[] elements; private int count; public void Add(T element) { if (count == elements.Length) Resize(count * 2); elements[count++] = element; } public T this[int index] { get { return elements[index]; } set { elements[index] = value; } public int Count { get { return count; } List<int> intList = new List<int>(); intList.Add(1); // No boxing intList.Add(2); // No boxing intList.Add("Three"); // Compile-time error int i = intList[0]; // No cast required List intList = new List(); intList.Add(1); intList.Add(2); intList.Add("Three"); int i = (int)intList[0]; List intList = new List(); intList.Add(1); // Argument is boxed intList.Add(2); // Argument is boxed intList.Add("Three"); // Should be an error int i = (int)intList[0]; // Cast required © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Generics Why generics? How are C# generics implemented? 1/14/2019 1:33 AM Generics Why generics? Type checking, no boxing, no downcasts Reduced code bloat (typed collections) How are C# generics implemented? Instantiated at run-time, not compile-time Checked at declaration, not instantiation Work for both reference and value types Complete run-time type information © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Generics Type parameters can be applied to Class, struct, interface, delegate types class Dictionary<K,V> {...} struct HashBucket<K,V> {...} interface IComparer<T> {...} delegate R Function<A,R>(A arg); Dictionary<string,Customer> customerLookupTable; Dictionary<string,List<Order>> orderLookupTable; Dictionary<string,int> wordCount; © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Generics Type parameters can be applied to Class, struct, interface, delegate types Methods class Utils { public static T[] CreateArray<T>(int size) { return new T[size]; } public static void SortArray<T>(T[] array) { ... string[] names = Utils.CreateArray<string>(10); names[0] = "Jones"; ... Utils.SortArray(names); © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Generics Type parameters can be applied to Class, struct, interface, delegate types Methods Type parameters can have constraints class Dictionary<K,V>: IDictionary<K,V> where K: IComparable<K> where V: IKeyProvider<K>, IPersistable, new() { public void Add(K key, V value) { ... } class Dictionary<K,V> where K: IComparable { public void Add(K key, V value) { ... if (key.CompareTo(x) == 0) {...} } class Dictionary<K,V> { public void Add(K key, V value) { ... if (((IComparable)key).CompareTo(x) == 0) {...} } © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Generics Zero or one primary constraint 1/14/2019 1:33 AM Generics Zero or one primary constraint Actual class, class, or struct Zero or more secondary constraints Interface or type parameter Zero or one constructor constraint new() class Link<T> where T: class {...} class Nullable<T> where T: struct {...} class Relation<T,U> where T: class where U: T {...} © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Generics Collection classes Collection interfaces 1/14/2019 1:33 AM Generics List<T> Dictionary<K,V> SortedDictionary<K,V> Stack<T> Queue<T> Collection classes Collection interfaces Collection base classes Utility classes Reflection IList<T> IDictionary<K,V> ICollection<T> IEnumerable<T> IEnumerator<T> IComparable<T> IComparer<T> Collection<T> KeyedCollection<T> ReadOnlyCollection<T> Nullable<T> EventHandler<T> Comparer<T> © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Anonymous Methods class MyForm : Form { ListBox listBox; 1/14/2019 1:33 AM Anonymous Methods class MyForm : Form { ListBox listBox; TextBox textBox; Button addButton; public MyForm() { listBox = new ListBox(...); textBox = new TextBox(...); addButton = new Button(...); addButton.Click += delegate { listBox.Items.Add(textBox.Text); }; } class MyForm : Form { ListBox listBox; TextBox textBox; Button addButton; public MyForm() { listBox = new ListBox(...); textBox = new TextBox(...); addButton = new Button(...); addButton.Click += new EventHandler(AddClick); } void AddClick(object sender, EventArgs e) { listBox.Items.Add(textBox.Text); © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Anonymous Methods Allows code block in place of delegate 1/14/2019 1:33 AM Anonymous Methods Allows code block in place of delegate Delegate type automatically inferred Code block can be parameterless Or code block can have parameters In either case, return types must match button.Click += delegate { MessageBox.Show("Hello"); }; button.Click += delegate(object sender, EventArgs e) { MessageBox.Show(((Button)sender).Text); }; © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Anonymous Methods Code block can access local variables 1/14/2019 1:33 AM Anonymous Methods Code block can access local variables public class Bank { List<Account> GetLargeAccounts(double minBalance) { Helper helper = new Helper(); helper.minBalance = minBalance; return accounts.FindAll(helper.Matches); } internal class Helper internal double minBalance; internal bool Matches(Account a) { return a.Balance >= minBalance; } } public class Bank { List<Account> accounts; List<Account> GetOverdrawnAccounts() { return accounts.FindAll(delegate(Account a) { return a.Balance < 0; }); } List<Account> GetLargeAccounts(double minBalance) { return a.Balance >= minBalance; delegate bool Predicate<T>(T item); public class List<T> { public List<T> FindAll(Predicate<T> filter) { List<T> result = new List<T>(); foreach (T item in this) { if (filter(item)) result.Add(item); } return result; © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Anonymous Methods Method group conversions 1/14/2019 1:33 AM Anonymous Methods Method group conversions Delegate type inferred when possible using System; using System.Threading; class Program { static void Work() {...} static void Main() { Thread t = new Thread(new ThreadStart(Work)); t.Start(); } using System; using System.Threading; class Program { static void Work() {...} static void Main() { Thread t = new Thread(Work); t.Start(); } © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Generics Performance 1/14/2019 1:33 AM © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Nullable Types System.Nullable<T> 1/14/2019 1:33 AM Nullable Types System.Nullable<T> Provides nullability for any value type Struct that combines a T and a bool public struct Nullable<T> where T: struct { public Nullable(T value) {...} public T Value { get {...} } public bool HasValue { get {...} } ... } Nullable<int> x = new Nullable<int>(123); ... if (x.HasValue) Console.WriteLine(x.Value); © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Nullable Types T? same as System.Nullable<T> null literal conversions Nullable conversions int? x = 123; double? y = 1.25; int? x = null; double? y = null; int i = 123; int? x = i; // int --> int? double? y = x; // int? --> double? int? z = (int?)y; // double? --> int? int j = (int)z; // int? --> int © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Nullable Types Lifted conversions and operators Comparison operators 1/14/2019 1:33 AM Nullable Types Lifted conversions and operators Comparison operators Null coalescing operator int? x = GetNullableInt(); int? y = GetNullableInt(); int? z = x + y; int? x = GetNullableInt(); if (x == null) Console.WriteLine("x is null"); if (x < 0) Console.WriteLine("x less than zero"); int? x = GetNullableInt(); int i = x ?? 0; © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Iterators foreach relies on “enumerator pattern” 1/14/2019 1:33 AM Iterators foreach relies on “enumerator pattern” GetEnumerator() method foreach makes enumerating easy But enumerators are hard to write! foreach (object obj in list) { DoSomething(obj); } Enumerator e = list.GetEnumerator(); while (e.MoveNext()) { object obj = e.Current; DoSomething(obj); } © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Iterators public class ListEnumerator : IEnumerator { List list; 1/14/2019 1:33 AM Iterators public class ListEnumerator : IEnumerator { List list; int index; internal ListEnumerator(List list) { this.list = list; index = -1; } public bool MoveNext() { int i = index + 1; if (i >= list.count) return false; index = i; return true; public object Current { get { return list.elements[index]; } public class List { internal object[] elements; internal int count; public IEnumerator GetEnumerator() { return new ListEnumerator(this); } public class List { internal object[] elements; internal int count; public IEnumerator GetEnumerator() { for (int i = 0; i < count; i++) { yield return elements[i]; } © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

1/14/2019 1:33 AM Iterators public IEnumerator GetEnumerator() { return new __Enumerator(this); } private class __Enumerator : IEnumerator { object current; int state; public bool MoveNext() { switch (state) { case 0: current = "Hello"; state = 1; return true; case 1: current = "World"; state = 2; return true; default: return false; public object Current { get { return current; } Method that incrementally computes and returns a sequence of values yield return and yield break Must return IEnumerator or IEnumerable public class Test { public IEnumerator GetEnumerator() { yield return "Hello"; yield return "World"; } © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Iterators public class List<T> { 1/14/2019 1:33 AM Iterators public class List<T> { public IEnumerator<T> GetEnumerator() { for (int i = 0; i < count; i++) yield return elements[i]; } public IEnumerable<T> Descending() { for (int i = count - 1; i >= 0; i--) public IEnumerable<T> Subrange(int index, int n) { for (int i = 0; i < n; i++) yield return elements[index + i]; List<Item> items = GetItemList(); foreach (Item x in items) {...} foreach (Item x in items.Descending()) {...} foreach (Item x in Items.Subrange(10, 20)) {...} © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Partial Types public partial class Customer { private int id; 1/14/2019 1:33 AM Partial Types public partial class Customer { private int id; private string name; private string address; private List<Orders> orders; } public class Customer { private int id; private string name; private string address; private List<Orders> orders; public void SubmitOrder(Order order) { orders.Add(order); } public bool HasOutstandingOrders() { return orders.Count > 0; public partial class Customer { public void SubmitOrder(Order order) { orders.Add(order); } public bool HasOutstandingOrders() { return orders.Count > 0; © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Static Classes Only static members 1/14/2019 1:33 AM Static Classes Only static members Cannot be used as type of variable, parameter, field, property, … Examples include System.Console, System.Environment public static class Math { public static double Sin(double x) {...} public static double Cos(double x) {...} ... } © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Property Accessors Different accessor accessibility 1/14/2019 1:33 AM Property Accessors Different accessor accessibility One accessor can be restricted further Typically set {…} more restricted public class Customer { private string id; public string CustomerId { get { return id; } internal set { id = value; } } © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

1/14/2019 1:33 AM External Aliases Enables use of identically named types in different assemblies namespace Stuff { public class Utils public static void F() {...} } foo.dll extern alias Foo; extern alias Bar; class Program { static void Main() { Foo.Stuff.Utils.F(); Bar.Stuff.Utils.F(); } namespace Stuff { public class Utils public static void F() {...} } bar.dll C:\>csc /r:Foo=foo.dll /r:Bar=bar.dll test.cs © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Namespace Alias Qualifiers Enables more version resilient code A::B looks up A only as alias global::X looks up in global namespace using IO = System.IO; class Program { static void Main() { IO::Stream s = new IO::File.OpenRead("foo.txt"); global::System.Console.WriteLine("Hello"); } © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Inline Warning Control 1/14/2019 1:33 AM Inline Warning Control #pragma warning using System; class Program { [Obsolete] static void Foo() {} static void Main() { #pragma warning disable 612 Foo(); #pragma warning restore 612 } © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Fixed Size Buffers C style arrays in unsafe code 1/14/2019 1:33 AM Fixed Size Buffers C style arrays in unsafe code public struct OFSTRUCT { public byte cBytes; public byte fFixedDisk; public short nErrCode; private int Reserved; public fixed char szPathName[128]; } © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Want to know more? Book Signing Cabana Session 1/14/2019 1:33 AM Want to know more? http://msdn.microsoft.com/vcsharp/language Book Signing Wednesday 12:30 – 1:30 Cabana Session Wednesday 2:00 – 3:15 Cabana 5 © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

Please fill out a session evaluation on CommNet 1/14/2019 1:33 AM Please fill out a session evaluation on CommNet Q1: Overall satisfaction with the session Q2: Usefulness of the information Q3: Presenter’s knowledge of the subject Q4: Presenter’s presentation skills Q5: Effectiveness of the presentation © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

© 2004 Microsoft Corporation. All rights reserved. 1/14/2019 1:33 AM © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary. © 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.