.NET Framework Class Library

.NET Framework Class Library Mark SapossnekCS 594 Computer Science Department Metropolitan College Boston University

Prerequisites • This module assumes you understand the fundamentals of: • Programming • Variables • Statements • Functions • Loops • Object-oriented programming • Classes • Inheritance • Polymorphism • Members • C#

Learning Objectives • Gain an overview of various .NET Framework classes and interfaces • Be able to write programs using these classes and interfaces

Agenda • Introduction • System Namespace • Collection Classes • I/O and Networking • Threading and Synchronization • Transactions • Exceptions

Introduction • Looking Back • The Microsoft .NET Framework Class Library • Benefits of the .NET Framework Class Library

IntroductionLooking Back • Language-dependent runtime libraries • C Runtime Library • C++ Standard Template Library • Visual Basic Runtime • Discriminatory access to functionality • Many APIs unsupported by Visual Basic • Advanced tasks often require C/C++ • Core functionality scattered all over Windows • COM/COM+, ActiveX controls, System DLLs, SDKs, IE • Multi-language development was difficult • COM/COM+ Libraries were unorganized • Extending existing classes was difficult

Introduction.NET Framework Class Library • One-stop, well-organized class framework • O/S-independent subset submitted to ECMA • Standardization backed by Microsoft, HP, Intel • Subset includes most things covered here • http://msdn.microsoft.com/net/ecma/ • Integrates all current Windows technologies • Everything in one place – for all languages • Windows Forms, GDI+, printing for Windows development • Web Forms, Web Services, networking for web development • Supports Active Directory, WMI, MSMQ, Services

IntroductionBenefits • Cross-language interoperability • Simplifies multi-language development, effectively providing a common language API • Supplies a standard set of classes, interfaces, and structures for any language targeting .NET CLR • Consistent and unified programming model • Replaces many existing COM libraries • Object-oriented and extensible class library • Inheritance, polymorphism and method overloading • Abstract base classes, Interfaces

System Namespace • System.Object • The not-so-primitive "primitive" types • String and text classes • Dates, times, and calendars • System console support • Standard interfaces

System NamespaceNamespaces Example Namespace MyProject { using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; Using System.Data … Public class Form1 : Form … }

System NamespaceSystem.Object • Base class for each and every type • Inheritance from System.Object is typically implicit • All simple and complex types share the same base • Single base class makes framework consistent • Collection classes can be used for everything • Intrinsic model for handling variant types • Strongly typed--no pointers, no structures • Much less error-prone than COM's VARIANT type • System.Object is a reference type • Value types (internally) inherit from ValueType • Special class derived from Object

System NamespaceSystem.Object Methods • System.Object.Equals(Object o) • Test if two types are equal • System.Object.ReferenceEquals(Object o) • Test if two references are to the same object • System.Object.Finalize() • To be overridden by subclasses. • Called when object is garbage collected • System.Object.GetHashCode() • Used with System.Collections.HashTable • Should be overriden to return good hashes • Good hash distribution speeds up hash tables • Default implementation: identity-based hash

System NamespaceSystem.Object Methods • System.Object.GetType() • Retrieves the type object for the object's class • GetType() is the entry point for .NET Reflection • System.Object.MemberwiseClone() • Creates an exact clone of this object • Works through Reflection with any class • ToString() • To be overriden; returns text representation • Default returns qualified name of this class • Not designed for user messages (use IFormattable)

System NamespaceSystem.Object Examples Public class Person { String name; public override string ToString(){ return name; } } Name n1 = new Name(“Fred”); Name n2 = new Name(“Fred”); Name n3 = n2; //n2 & n3 point to the same object if (n1 == n2) … // false if (n2 == n3) … // true if (n1.Equals(n2)) … // true if (n2.Equals(n3)) … // true

System Namespace“Primitive” Types • Traditionally perceived as "magic" or "special" • There is no primitive-type magic in .NET! • Very Smalltalk-like model • "Primitive" types are regular framework types • Still exposed as language-intrinsic types • C#: bool, int, long, string, double, float... • Visual Basic.NET: Boolean, Integer, String... • "Primitives" are mostly value-types • Exception: System.String is reference type • "Primitive" Types are not so primitive anymore • Full-featured classes, rich functionality

System NamespaceSystem.String • System.String is the cross-language string • One storage method, one API, unified handling • Locale-aware, always Unicode • String is immutable • Methods that appear to modify a String actually construct a new one • Use String.Format or StringBuilder class instead of string concatenation • Strings can be interned • One standard copy is kept • Can compare references

System NamespaceSystem.String • Fully featured string-handling capabilities • Forward and reverse substring searches • IndexOf(), LastIndexOf(), StartsWith(), EndsWith() • Whitespace stripping and padding • Trim(), PadLeft(), PadRight() • Range manipulation and extraction • Insert(), Remove(), Replace(), Substring(), Join(), Split() • Character casing and advanced formatting • ToLower(), ToUpper() • Format() much like C's printf but safe

System NamespaceSystem.String Example // string comparison Public static int Main() { string s =“abc”; string s1; s1 = s; // s1 and s refer to the same object string s2 = “abc”; if (s1 == s2) Console.WriteLine(“Strings are equal”); else Console.WriteLine(“This shouldn’t happen!”); return 0 }

System NamespaceSystem.Text.StringBuilder • Efficient way to build up a string by concatenating, replacing, inserting and removing substrings • Automatically increases buffer size • Can control manually too

System NamespaceOther Core Types • System.Byte, System.SByte – Single byte numeric • System.Char – Single Unicode character • System.Boolean – True or False logical value • System.Guid • 128-bit, universally unique identifier • Built-in generator: System.Guid.NewGuid() • Intrinsic conversions to and from strings, byte arrays • The "Nothings" • System.DBNull – database-equivalent NULL type • System.Empty – like COM's VT_EMPTY • System.Missing – used with optional args

System NamespaceDate and Time Support • System.DateTime struct for dates and times • Virtually unlimited date values (100 AD to 9999 AD) • Date and Time arithmetics built-in • AddDays(), AddSeconds()... • Sophisticated, locale-aware formatting and parsing • System.TimeSpan struct for durations • Can represent arbitrary timespans • Can express span in aribitary units by conversion • System.TimeZone for time-zone support

System NamespaceSystem.Console • System.Console class for console I/O • Supports standard in, standard out, standard error • Writing to the console • Write() or WriteLine() • Supports String.Format syntax • Reading from the console • Read() reads on characters • ReadLine() reads one full line Console.Write("Snow White and the {0} dwarfs", 7);

System NamespaceOther System Goodies • System.URI class • Two-way parsing and construction of URIs • System.Random class • Random number generator • System.Convert class • One-stop place for core type conversions

System NamespaceStandard Interfaces • IFormattable: Provides functionality to format the value of an object • Format method: Formats the value of the current instance as specified. • IDisposable: Provides explicit control of releasing resources

System NamespaceString.Format and IFormattable • String.Format • Implement IFormattable for custom formatting of your own types • Use IServiceProvider to get culturally-aware delimiters for numbers and date/time • Implement ICustomFormatter to override default formatting for built-in types String.Format(“Please order {0} widgets at {1} each.”, i, f); String.Format(“{0:U}”, DateTime.Now); interface IFormattable { String Format(String format, IServiceObjectProvider sop);}

System NamespaceIDisposable Example class ResourceWrapper : IDisposable { private IntPrt handle; // Pointer to an external resourceprivate OtherResource otherRes; bool disposed = false; private void freeState () { // Free your own state if (!disposed) { CloseHandle (handle); dispose = true; } } // Free your own state, call dispose on all state you hold, // and take yourself off the Finalization queue public void Dispose () { freeState(); OtherRes.Dispose(); GC.Suppress.Finalization(this); } // Free your own state (NOT other state you hold) and // give your parent a chance to finalize public void Finalize () { freeState(); Base.Finalize(); }

Collection Classes • Arrays • Collection Interfaces • The Collection Classes

Collection ClassesArrays • The only collection outside Collections namespace • System.Array class • Mapped to language-intrinsic arrays • Polymorphic, stores System.Object elements • Arbitrary number of dimensions, lengths • Specified at creation time (CreateInstance) • After construction, array dimensions are fixed • Supports sorting • Self-comparing IComparable objects • External comparisons with IComparer • Supports binary searches on sorted arrays

Collection ClassesArrays Example public static void Main() { // Create and initialize a new int array and a new Object array. int[] myIntArray = new int[5] { 1, 2, 3, 4, 5 }; Object[] myObjArray = new Object[5] { 26, 27, 28, 29, 30 }; // Copy the first two elements from the int array to the Object array. Array.Copy( myIntArray, myObjArray, 2 ); // Print the values of the modified arrays. Console.WriteLine( "\nAfter copying the first two elements of the int array to the Object array," ); Console.Write( "int array: " ); PrintValues( myIntArray ); Console.Write( "Object array:" ); PrintValues( myObjArray ); // Copy the last two elements from the Object array to the int array. Array.Copy( myObjArray, myObjArray.GetUpperBound(0) - 1, myIntArray, myIntArray.GetUpperBound(0) - 1, 2 ); }

Collection ClassesCollections Interfaces • IEnumerable • Supports simple iteration over the collection • GetEnumerator() returns IEnumerator iterator • IEnumerator: Current, MoveNext(), Reset() • IEnumerator • Iterator for enumerable collections • Properties and methods: Current(), MoveNext(), Reset()

Collection ClassesEnumerating a Set of Items • All types offer standard mechanism for item iteration • System.Collections.IEnumerable interface • GetEnumerator returns object dedicated to item iteration public interface IEnumerable { IEnumerator GetEnumerator();} public interface IEnumerator { Boolean MoveNext(); Object Current { get; } void Reset();}

Collection ClassesIEnumerable and IEnumerator // Construct a type that manages a set of items// This type must offer a public GetEnumerator methodSetType st = new SetType(...);// To enumerate items, request the enumeratorIEnumerator e = st.GetEnumerator();// Advance enumerator’s cursor until no more itemswhile (e.MoveNext()) { // Cast the Current item to the proper type ItemType it = (ItemType) e.Current; // Use the item any way you want Console.WriteLine(“Do something with this item: “ + it);}

Collection ClassesCollections Interfaces • ICollection (derived from IEnumerable) • Basic collection interface: Count(), CopyTo(), IsSynchronized() • IDictionary (derived from ICollection) • Basic association container interface • Keys / Values table implementation • Item indexer looks up a value given its key • Add(), Remove(), Contains() and Clear() methods • IList (derived from ICollection) • A collection whose objects can be individually indexed • Item indexer looks up a value given its index • Add(), Remove(), Contains() and Clear() methods

Collection ClassesCollection Classes • System.Collections.ArrayList • Dynamic arrays implementing IList • Can grow and shrink in size (unlike System.Array) • System.Collections.BitArray • Compact array of bits • System.Collections.HashTable • Fast hash-table implementing IDictionary • Uses HashCode of object • There is no Dictionary class; use HashTable • System.Collections.SortedList • Auto-sorted, string- and integer- indexed collection • No duplicates

Collection ClassesSystem.Collections.ArrayList using System; using System.Collections; public class SampleArrayList { public static void Main() { // Create and initialize a new ArrayList. ArrayList myAL = new ArrayList(); myAL.Add("Hello"); myAL.Add("World"); myAL.Add("!"); // Display the properties and values. Console.WriteLine( "myAL" ); Console.WriteLine( "\tCount: {0}", myAL.Count ); Console.WriteLine( "\tCapacity: {0}", myAL.Capacity ); Console.Write( "\tValues:" ); PrintValues( myAL );} public static void PrintValues( IEnumerable myList ) { System.Collections.IEnumerator myEnumerator = myList.GetEnumerator(); while ( myEnumerator.MoveNext() ) Console.Write("\t{0}", myEnumerator.Current ); Console.WriteLine(); } }

Collection ClassesOther Collection Classes • System.Collections.Stack • Stack implementation with Push() and Pop() • Fully enumerable (implements IEnumerable) • System.Collections.Queue • Queue with Dequeue() and Enqueue() • Fully enumerable

Collection ClassesSystem.Collections.Stack using System; using System.Collections; public class SamplesStack { public static void Main() { // Create and initialize a new Stack. Stack myStack = new Stack(); myStack.Push("Hello"); myStack.Push("World"); myStack.Push("!"); Console.WriteLine( "myStack" ); Console.WriteLine( "\tCount: {0}", myStack.Count ); Console.Write( "\tValues:" ); PrintValues( myStack ); } public static void PrintValues( IEnumerable myCollection ) { System.Collections.IEnumerator myEnumerator = myCollection.GetEnumerator(); while ( myEnumerator.MoveNext() ) Console.Write( "\t{0}", myEnumerator.Current ); Console.WriteLine(); } }

Collection ClassesSystem.Collections.Queue using System; using System.Collections; public class SamplesQueue { public static void Main() { Queue myQ = new Queue(); myQ.Enqueue("Hello"); myQ.Enqueue("World"); myQ.Enqueue("!"); Console.WriteLine( "myQ" ); Console.WriteLine( "\tCount: {0}", myQ.Count ); Console.Write( "\tValues:" ); PrintValues( myQ ); } public static void PrintValues( Ienumerable myCollection ) { System.Collections.IEnumerator myEnumerator = myCollection.GetEnumerator(); while ( myEnumerator.MoveNext() ) Console.Write( "\t{0}", myEnumerator.Current ); Console.WriteLine(); } }

Collection ClassesSystem.Collections.Specialized • NameObjectCollectionBase • Abstract class, indexed view on HashTable • Combines indexed order with Hashtable-speed • NameValueCollection • Sorted collection of string values and string keys • StringDictionary • Unsorted, string values and string keys

I/O and Networking • Directories and Files • Streams, Stream Readers and Stream Writers • Networking Support

I/O and NetworkingDirectories and Files • Provides a fully object-oriented way to explore the file system • System.IO.Directory and System.IO.File provide static methods to manipulate directories and files, respectively • System.IO.DirectoryInfo and System.IO.FileInfo provide instance methods to manipulate directories and files, respectively

I/O and NetworkingDirectories and Files • System.IO.DirectoryInfo represents a directory • GetDirectories([mask]) gets subdirectories • GetFiles([mask]) gets contained files • System.IO.FileInfo represents a file • Can construct directly by providing a path • Or returned from GetFiles() enumeration • All OpenX() methods return System.IO.Stream • Open(), OpenRead(), OpenWrite(), OpenText()

I/O and NetworkingStreams • Abstract base stream: System.IO.Stream • Read(), Write() for basic synchronous access • Full asynchronous support • Call BeginRead() or BeginWrite() and pass callback • Callback is invoked as soon as data is received. • Asynchronous call completed with EndRead()/EndWrite() • System.IO.FileStream • Can open and access files directly • Actual type returned by File.Open() • System.IO.MemoryStream • Constructs a stream in-memory

I/O and NetworkingStream Readers • Higher level access to Stream reading functions • System.IO.BinaryReader • Designed for typed access to stream contents • Read methods for most core data types • ReadInt16(), ReadBoolean(), ReadDouble(), etc. • System.IO.TextReader • Abstract base class for reading strings from streams • System.IO.StreamReader (inherits TextReader) • ReadLine() reads to newline • ReadToEnd() reads full stream into string • System.IO.StringReader (inherits TextReader) • Simulates stream input from string

I/O and NetworkingStream Writers • High-level access to Stream writing functions • System.IO.BinaryWriter • Designed for typed writes to streams • >15 strongly typed overloads for Write() method • System.IO.TextWriter • Abstract base class for writing strings to streams • Includes placeholder-formatted strings • System.IO.StreamWriter (inherits TextWriter) • Writes strings to streams with encoding support • System.IO.StringWriter • Simulates streams--writes on an output string

I/O and NetworkingStream Reader Example // Reading Text Files File fIn = NewFile(“C:\\dotNet Projects\\Readme.txt”); StreamRead strm = fIn.OpenText(); String sLine; do { sLine = strm.ReadLine(); AddItem(sLine); } while (sLine != null); Strm.close();

I/O and NetworkingStream Writer Example public class MyWriter { private Stream s; public MyWriter(Stream stream) { s = stream; } public void WriteDouble(double myData) { byte[] b = myData.GetBytes(); // GetBytes is a binary representation of // a double data type. s.Write(b,0,b.Length); } public void Close() { s.Close(); } }

.NET Framework Class Library