Overview of Visual C# 2005 Henrik Westergaard Hansen

Agenda Generics Nullable Types Anonymous methods Iterators Partial types Other enhancements IDE Enhancements

public class List { private object[] elements; private object[] elements; private int count; private int count; public void Add(object element) { public void Add(object element) { if (count == elements.Length) Resize(count * 2); if (count == elements.Length) Resize(count * 2); elements[count++] = element; elements[count++] = element; } public object this[int index] { public object this[int index] { get { return elements[index]; } get { return elements[index]; } set { elements[index] = value; } set { elements[index] = value; } } public int Count { public int Count { get { return count; } get { return count; } }} Generics public class List public class List { private T[] elements; private T[] elements; private int count; private int count; public void Add(T element) { public void Add(T element) { if (count == elements.Length) Resize(count * 2); if (count == elements.Length) Resize(count * 2); elements[count++] = element; elements[count++] = element; } public T this[int index] { public T this[int index] { get { return elements[index]; } get { return elements[index]; } set { elements[index] = value; } set { elements[index] = value; } } public int Count { public int Count { get { return count; } get { return count; } }} 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 List intList = new List (); intList.Add(1);// No boxing intList.Add(2);// No boxing intList.Add("Three");// Compile-time error int i = intList[0];// No cast required

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

Generics Type parameters can be applied to Class, struct, interface, and delegate types class Dictionary {…} struct HashBucket {…} interface IComparer {…} delegate R Function (A arg); Dictionary customerLookupTable; Dictionary > orderLookupTable; Dictionary numberSpellings;

Generics Type parameters can be applied to Class, struct, interface, and delegate types Methods class Utils { public static T[] CreateArray (int size) { public static T[] CreateArray (int size) { return new T[size]; return new T[size]; } public static void SortArray (T[] array) { public static void SortArray (T[] array) { … }} string[] names = Utils.CreateArray (3); names[0] = "Jones"; names[1] = "Anderson"; names[2] = "Williams"; Utils.SortArray(names);

Generics Type parameters can be applied to Class, struct, interface, and delegate types Methods Type parameters can have constraints One base class, multiple interfaces, new()

Generics class Dictionary class Dictionary { public void Add(K key, V value) { public void Add(K key, V value) { … if (((IComparable)key).CompareTo(x) == 0) {…} if (((IComparable)key).CompareTo(x) == 0) {…} … }} class Dictionary where K: IComparable { public void Add(K key, V value) { public void Add(K key, V value) { … if (key.CompareTo(x) == 0) {…} if (key.CompareTo(x) == 0) {…} … }} class Dictionary : IDictionary class Dictionary : IDictionary where K: IComparable where K: IComparable where V: IKeyProvider, IPersistable, new() where V: IKeyProvider, IPersistable, new() { public void Add(K key, V value) { … }}

public class List public class List { public void Add(T item) {…} public void Add(T item) {…} public T this[int index] {…} public T this[int index] {…} …} public class List : IList { public void Add(T item) {…} public void Add(T item) {…} public T this[int index] {…} public T this[int index] {…} …} public interface IList { public void Add(object item); public void Add(object item); public object this[int index] {…} public object this[int index] {…} …} Generics Generics are “invariant” Interfaces can be used for type neutrality List<object>List<int>List<string> object

Generics T.default Null checks Type casts void Foo () { T x = null;// Error (if T.valuetype) T x = null;// Error (if T.valuetype) T y = T.default;// Ok T y = T.default;// Ok} void Foo (T x) { if (x == null) { if (x == null) { throw new FooException(); throw new FooException(); } …} void Foo (T x) { int i = (int)x;// Error int i = (int)x;// Error int j = (int)(object)x;// Ok int j = (int)(object)x;// Ok}

Generics Collection classes Collection interfaces Collection base classes Utility classes Reflection Native support in IL and CLR LinkedList List LinkedList List Dictionary<K,V>SortedDictionary<K,V>Stack<T>Queue<T> 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>

Generics System.Nullable<T> Provides nullability for any type Struct that combines a T and a bool Conversions between T and Nullable Conversions between T and Nullable Conversion from null literal to Nullable Conversion from null literal to Nullable Nullable x = 123; Nullable y = null; int i = (int)x; int j = x.Value; if (x.HasValue) Console.WriteLine(x.Value); Console.WriteLine(x.Value);

Nullable Types T? same as System.Nullable T? same as System.Nullable 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

Anonymous Methods class MyForm : Form { ListBox listBox; ListBox listBox; TextBox textBox; TextBox textBox; Button addButton; Button addButton; public MyForm() { public MyForm() { listBox = new ListBox(...); listBox = new ListBox(...); textBox = new TextBox(...); textBox = new TextBox(...); addButton = new Button(...); addButton = new Button(...); addButton.Click += new EventHandler(AddClick); addButton.Click += new EventHandler(AddClick); } void AddClick(object sender, EventArgs e) { void AddClick(object sender, EventArgs e) { listBox.Items.Add(textBox.Text); listBox.Items.Add(textBox.Text); }} class MyForm : Form { ListBox listBox; ListBox listBox; TextBox textBox; TextBox textBox; Button addButton; Button addButton; public MyForm() { public MyForm() { listBox = new ListBox(...); listBox = new ListBox(...); textBox = new TextBox(...); textBox = new TextBox(...); addButton = new Button(...); addButton = new Button(...); addButton.Click += delegate { addButton.Click += delegate { listBox.Items.Add(textBox.Text); listBox.Items.Add(textBox.Text); }; }; }}

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); };

Generic Delegates and List Methods System.Action - Performs an action on the specified object List.ForEach - Performs specified action on each element System.Predicate - Defines a set of criteria data must meet List.Find/FindIndex/FindAll/FindLast – Filters data based on predicate List.TrueForAll - Determines whether every element meets criteria in predicate public sealed delegate void Action ( T obj ); public sealed delegate bool Predicate ( T obj ); public T Find( Predicate match ); public void ForEach( Action action ); public bool TrueForAll( Predicate match );

Using Anonymous Methods List numbers = new List (); numbers.Add(1);numbers.Add(1); numbers.Add(6); numbers.Add(2); int sum = 0; numbers.ForEach(delegate(int i) { sum += i; }); { sum += i; }); Console.WriteLine(sum); //Print 10 int match = numbers.FindIndex(delegate(int i) { return i == 6; }); { return i == 6; }); Console.WriteLine(match); //Print 2 bool check = numbers.TrueForAll(delegate(int i) { return i > 0; }); { return i > 0; }); Console.WriteLine(check); //Print True ForEach FindIndex TrueForAll Generic List

Demo #1 Generics Performance

Iterators foreach relies on “enumerator pattern” GetEnumerator() method foreach makes enumerating easy foreach (object obj in list) { DoSomething(obj); DoSomething(obj);} Enumerator e = list.GetEnumerator(); while (e.MoveNext()) { object obj = e.Current; object obj = e.Current; DoSomething(obj); DoSomething(obj);}

Iterators public class List { internal object[] elements; internal object[] elements; internal int count; internal int count; public ListEnumerator GetEnumerator() { return new ListEnumerator(this); public ListEnumerator GetEnumerator() { return new ListEnumerator(this); }} public class ListEnumerator : IEnumerator { List list; List list; int index; int index; internal ListEnumerator(List list) { internal ListEnumerator(List list) { this.list = list; this.list = list; index = -1; index = -1; } public bool MoveNext() { public bool MoveNext() { int i = index + 1; int i = index + 1; if (i >= list.count) return false; if (i >= list.count) return false; index = i; index = i; return true; return true; } public object Current { public object Current { get { return list.elements[index]; } get { return list.elements[index]; } }}

public class List { public IEnumerator GetEnumerator() { public IEnumerator GetEnumerator() { for (int i = 0; i < count; i++) { yield return elements[i]; for (int i = 0; i < count; i++) { yield return elements[i]; } }} Iterators Method that incrementally computes and returns a sequence of values yield return and yield break Must return IEnumerator or IEnumerable public IEnumerator GetEnumerator() { return new __Enumerator(this); return new __Enumerator(this);} private class __Enumerator: IEnumerator { object current; object current; int state; int state; public bool MoveNext() { public bool MoveNext() { switch (state) { switch (state) { case 0: … case 0: … case 1: … case 1: … case 2: … case 2: … … } } public object Current { public object Current { get { return current; } get { return current; } }}

public class List public class List { public IEnumerator GetEnumerator() { public IEnumerator GetEnumerator() { for (int i = 0; i < count; i++) yield return elements[i]; for (int i = 0; i < count; i++) yield return elements[i]; } public IEnumerable Descending() { public IEnumerable Descending() { for (int i = count - 1; i >= 0; i--) yield return elements[i]; for (int i = count - 1; i >= 0; i--) yield return elements[i]; } public IEnumerable Subrange(int index, int n) { public IEnumerable Subrange(int index, int n) { for (int i = 0; i < n; i++) yield return elements[index + i]; for (int i = 0; i < n; i++) yield return elements[index + i]; }} Iterators List items = GetItemList(); foreach (Item x in items) {…} foreach (Item x in items.Descending()) {…} foreach (Item x in Items.Subrange(10, 20)) {…}

Partial Types public partial class Customer { private int id; private int id; private string name; private string name; private string address; private string address; private List orders; private List orders;} public partial class Customer { public void SubmitOrder(Order order) { public void SubmitOrder(Order order) { orders.Add(order); orders.Add(order); } public bool HasOutstandingOrders() { public bool HasOutstandingOrders() { return orders.Count > 0; return orders.Count > 0; }} public class Customer { private int id; private int id; private string name; private string name; private string address; private string address; private List orders; private List orders; public void SubmitOrder(Order order) { public void SubmitOrder(Order order) { orders.Add(order); orders.Add(order); } public bool HasOutstandingOrders() { public bool HasOutstandingOrders() { return orders.Count > 0; return orders.Count > 0; }}

Other Enhancements Static classes Can contain only static members Cannot be type of variable, parameter, etc. System.Console, System.Environment, etc. public static class Math { public static double Sin(double x) {…} public static double Sin(double x) {…} public static double Cos(double x) {…} public static double Cos(double x) {…} …}

Other Enhancements Property accessor accessibility Allows one accessor to be restricted further Typically set {…} more restricted than get {…} public class Customer { private string id; private string id; public string CustomerId { public string CustomerId { get { return id; } get { return id; } internal set { id = value; } internal set { id = value; } }}

Other Enhancements Namespace alias qualifier A::B looks up A only as namespace alias global::X starts lookup in global namespace using IO System.IO; using IO = System.IO; class Program { static void Main() { static void Main() { IO::Stream s = new IO::File.OpenRead("foo.txt"); IO::Stream s = new IO::File.OpenRead("foo.txt"); global::System.Console.WriteLine("Hello"); global::System.Console.WriteLine("Hello"); }}

Other Enhancements Fixed size buffers C style embedded arrays in unsafe code public struct OFSTRUCT { public byte cBytes; public byte cBytes; public byte fFixedDisk; public byte fFixedDisk; public short nErrCode; public short nErrCode; private int Reserved; private int Reserved; public fixed char szPathName[128]; public fixed char szPathName[128];}

Other Enhancements #pragma warning Control individual warnings in blocks of code using System; class Program { [Obsolete] [Obsolete] static void Foo() {} static void Foo() {} static void Main() { static void Main() { #pragma warning disable 612 Foo(); Foo(); #pragma warning restore 612 }}

Visual Studio Team System Change ManagementWork Item TrackingReportingProject Portal Visual Studio Team Foundation Server Integration ServicesProject Management Process and Architecture Guidance Dynamic Code Analyzer Visual Studio Team Edition Software Architects Static Code AnalyzerCode ProfilerUnit TestingCode CoverageTeam Explorer (includes Team Foundation Server CAL)Visual Studio Professional EditionLoad TestingManual TestingTest Case ManagementApplication DesignerSystem DesignerLogical Datacenter Designer Visual Studio Team Edition Software Developers Visual Studio Team Edition Software Testers Visual Studio Industry Partners Team BuildClass Designer (in Visual Studio Standard Edition and higher) Deployment DesignerVisio for Enterprise Architects (in MSDN Premium Subscription)

Smart Clients Web Services & Offline/Online support Device Adaptability Tough to Deploy Heavy Footprint DLL Hell Network Dependency Poor User Experience Rich UI Complex To Develop Rich User Experience Developer Productivity Responsive Broad Reach Easy Change Management Ease of Deployment

Resources MSDN asp?url=/library/en- us/dnvs05/html/csharp_generics.asp asp?url=/library/en- us/dnvs05/html/csharp_generics.asp es/04/05/C20/default.aspx es/04/05/C20/default.aspx

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