Introduction Base Class Library
PV178: Programming for .NET Framework
CLI Libraries, Base Class Library
Vojtˇech Forejt, forejt@fi.muni.cz
Martin Osovsk´y, osovsky@ics.muni.cz
Faculty of Informatics and Institute of Computer Science
Masaryk University
February 26, 2009
Introduction Base Class Library
CLI Library ­ Goals
Standard library
Available for all .NET languages
CLS compliant (almost)
Consistent design patterns
Provide features similar to C Standard library of 1990
Support networking, XML, etc.
Introduction Base Class Library
Taxonomy
Libraries and Profiles
Library is specified by
Set of types
Set of CLI features
Modification to types from other libraries
CLI defines 7 libraries
Profile is a set of libraries
CLI defines 2 profiles: Kernel and Compact
Introduction Base Class Library
Taxonomy cont.Parallellibrary
Extendedarraylibrary
Floatingpointlibrary
Compact profile
Kernel profile
XML library
Network
library
Reflection
library
Runtime infrastructure library
Base class library
Introduction Base Class Library
Base Class Library ­ Namespaces
System
System.CodeDom
System.Collections
System.Diagnostics
System.Globalization
System.IO
System.Resources
System.Text
System.Text.RegularExpressions
Introduction Base Class Library
Arrays
Single-dimensional arrays
int [ ] arrayA = new int [ 5 ] ;
int [ ] arrayB = { 1 , 2 , 3 , 4 , 5 , 6 };
Introduction Base Class Library
Arrays
Single-dimensional arrays
int [ ] arrayA = new int [ 5 ] ;
int [ ] arrayB = { 1 , 2 , 3 , 4 , 5 , 6 };
Multi-dimensional
int [ , ] arrayC = new int [2 , 3 ] ;
int [ , ] arrayD = { { 1 , 2 , 3 } , { 4 , 5 , 6 } };
Introduction Base Class Library
Arrays
Single-dimensional arrays
int [ ] arrayA = new int [ 5 ] ;
int [ ] arrayB = { 1 , 2 , 3 , 4 , 5 , 6 };
Multi-dimensional
int [ , ] arrayC = new int [2 , 3 ] ;
int [ , ] arrayD = { { 1 , 2 , 3 } , { 4 , 5 , 6 } };
Jagged arrays
int [ ] [ ] arrayE = new int [ 5 ] [ ] ;
arrayE [ 0 ] = new int [ 2 ] ;
Introduction Base Class Library
Indexers
Allow instances of classes to be indexed like arrays
Like properties with parameters
public class MyCharArray
{
private char [ ] a r r ;
public MyCharArray () { . . . }
public char t h i s [ int i ]
{
get { return t h i s . a r r [ i ] ; }
set { t h i s . a r r [ i ] = value ; }
}
}
Introduction Base Class Library
System.Collections namespace
Collections
Represent data structures for storing multiple objects.
Two basic types in BCL: Lists, Dictionaries.
Lists Contains simple objects.
Dictionaries Contains key-values pairs.
Introduction Base Class Library
Enumeration
Enumeration and Iteration
Interface IEnumerable implements method IEnumerator
GetEnumerator();
Class implementing IEnumerator does the enumeration.
Boolean MoveNext() increments the index and returns true
if the element exists.
read-only property Object Current returns the object at the
index.
void Reset() sets the index to -1.
Introduction Base Class Library
Enumeration
Enumeration and Iteration
Interface IEnumerable implements method IEnumerator
GetEnumerator();
Class implementing IEnumerator does the enumeration.
Boolean MoveNext() increments the index and returns true
if the element exists.
read-only property Object Current returns the object at the
index.
void Reset() sets the index to -1.
Iterator is a section of code that returns an ordered sequence
of values of the same type
Uses yield return and yield break statements to return
elements and stop iterating
Must return IEnumerable or IEnumerator
Multiple iterators can be implemented in one class.
The IEnumerator class is generated by compiler
Introduction Base Class Library
Enumeration
Enumeration and Iteration cont.
Example Iteration
Introduction Base Class Library
Enumeration
Comparison
For sorted collections or sets we need comparison support.
Equality testing ­ virtual method Equals.
Comparison ­ IComparable interface
method int CompareTo() returns positive integer if value of
this is greater than argument's value, zero if they are equal
and negative integer otherwise.
Introduction Base Class Library
Enumeration
ICollection
Implements IEnumerable
Property int Count
Method void CopyTo(Array array, int index)
Members used for synchronization
Implementing classes
Stack Methods Push, Pop, Peek.
Queue Methods Enqueue and Dequeue.
BitArray Compact array of bit values.
Introduction Base Class Library
Enumeration
IList
Implements ICollection.
Important methods:
Add Adds an item
Clear Removes all items
Contains Determines whether a value is contained
IndexOf Returns index of first occurence of a value
Insert Inserts an item at the index
Remove Removes first occurence of the item
RemoveAt Removes the item at the index
Important properties:
IsFixedSize
IsReadOnly
Item Gets or sets the element at the index
Implementing class in BCL
ArrayList - Array whose size is dynamically increased as
required
Introduction Base Class Library
Enumeration
ArrayList
Example CollectionsExample.cs
Introduction Base Class Library
Enumeration
IDictionary
Implements ICollection
Important members
Item Gets or sets element with specified key.
Keys
Values
Add
Clear
Contains
Remove
Implementing classes in BCL
HashTable Key/value pairs organised based on the hash
code of the key.
SortedList Key/value pairs sorted by keys, accessible by key
and index.
Introduction Base Class Library
Enumeration
SortedList
Example CollectionsExample.cs
Introduction Base Class Library
Enumeration
Generic Collections
Namespace System.Collections.Generic
Defined with type parameters:
Interfaces IEnumerable<T>, IComparable<T>, IList<T>,
IDictionary<TKey, TValue>
Classes Dictionary<T>, SortedList<T>, Stack<T>,
Queue<T>
"New" classes: LinkedList, List, SortedDictionary
Introduction Base Class Library
System.IO namespace
System.IO Namespace ­ Overview
Reading and writing to streams and files
File and directory support
Introduction Base Class Library
System.IO namespace
Streams
Stream is a potentially infinite sequence of elements of certain
type.
Operate on a resource whose internal structure is hidden.
Basic operations: reading, writing.
Types:
binary vs. character vs. other
read-only vs. write-only vs. read/write
synchronous (blocking) vs. asynchronous (non-blocking)
sequential vs. random access
"low-level" vs. adapter streams
Introduction Base Class Library
System.IO namespace
System.IO.Stream Class
Abstract class
Basic methods and properties:
Write Write a block (array) of bytes to the stream.
WriteByte Write a single byte to the stream.
Read Read a block of bytes from the stream.
ReadByte Read a single byte from the stream.
Close Close the stream.
Seek Move the internal position pointer.
Flush Flush the internal cache.
CanRead
CanWrite
CanSeek
Position
Introduction Base Class Library
System.IO namespace
I/O Timeouts
Read(),Write() are blocking operations.
CanTimeout Does the stream support timeouts?
ReadTimeout read timeout (usually in ms).
WriteTimeout write timeout (usually in ms).
May utilize asynchronous streams (not in this lecture).
Introduction Base Class Library
System.IO namespace
Inheriting Classes
FileStream
Operates on file system file.
Allows to set access permissions in a constructor.
Support for seeking, no support for timeouts.
Introduction Base Class Library
System.IO namespace
Inheriting Classes
FileStream
Operates on file system file.
Allows to set access permissions in a constructor.
Support for seeking, no support for timeouts.
BufferedStream
Adapter stream.
Implements caching on a nested stream.
Buffer size may be set in constructor.
Introduction Base Class Library
System.IO namespace
Inheriting Classes
FileStream
Operates on file system file.
Allows to set access permissions in a constructor.
Support for seeking, no support for timeouts.
BufferedStream
Adapter stream.
Implements caching on a nested stream.
Buffer size may be set in constructor.
MemoryStream
Useful to compose data in memory.
Introduction Base Class Library
System.IO namespace
Stream Example
Example StreamsExample.
Introduction Base Class Library
System.IO namespace
System.IO.TextReader
Reading character data
Similar to Stream
Abstract class for StringReader and StreamReader.
Read Read single character
ReadBlock Read block (array) of characters
ReadLine Read single line as string
ReadToEnd Read to the end of reader and return as string
Introduction Base Class Library
System.IO namespace
System.IO.TextWriter
Writing character data
Similar to Stream
Abstract class for StringReader and StreamReader.
Write write single object (of various types)
WriteLine like Write, appends newline character
Introduction Base Class Library
System.IO namespace
StreamWriter Example
Example StreamWriterExample.
Introduction Base Class Library
System.IO namespace
Compression
adapter streams: DeflateStream, GZipStream
DeflateStream implements deflate algoritm
GZipStream as above, in standard format.
Introduction Base Class Library
System.IO namespace
Compression Example
Example Compress.
Introduction Base Class Library
System.IO namespace
Filesystem classes
Static File and non-static FileInfo classes
Copying, deleting, moving or creating files
Creating of FileStream
static Directory and non-static DirectoryInfo classes
Creating, moving, and enumerating through directories and
subdirectories
Introduction Base Class Library
System.IO namespace
Filesystem Example
Example FileSystemExamples