Bài giảng Lập trình C# 2010: Chương 4 - ĐH Công nghệ Đồng Nai

Bài giảng Lập trình C# 2010: Chương 4 trình bày về Using Arrays and Collections (Sử dụng mảng và Bộ sưu tập) như khái niệm, đặc điểm, cú pháp, thao tác thực hiện và các nội dung khác.

One Dimension Array

5 2 9 7 6 0 8

M[0] M[1] M[2] M[3] M[4] M[5] M[6]

- Same name

- Same type

- Get Element by Index ( 0 n-1)

One Dimension Array

• Programmer specifies the type of the elements

of the array

• new operator to allocate dynamically the

number of elements in the array

• Array declarations and initializations need not

be in the same statement

• In arrays of value types, each element contains

one value of the declared type

Declaring & Creating Arrays

int M1 [] =new int [ 10 ] ;

• array_name Length: return size of array

object at position index.

position index.

• array_name SetValue ( object value, int index):

add or modify an object at position index

object at position index

Properties & Methods

Passing Arrays to Method

• Pass arrays as arguments to methods by specifying the name of the array (no

brackets)

• Arrays are passed by reference

• Individual array elements are passed by

value

static void inputA rray(int[] arr)

{

Random ran = new Random ();

for ( int i = 0; i < arr.Length; i+ + )

arr[i] = ran.N ext(100);

}

Passing Arrays to Method

Using out or ref keyword to pass by reference

static void edit( out int n)

The out parameter must be assigned to before control leaves the current method

static void edit(out int n)

{

//n = -113;

}

 Compile error

edit( out arr[0]);

Tw o w ays: arr[0] -113

arr[0]= 100;

Multi Dimension

7 2 9

9 5 4

8 0 3

0 1 6

arrName = new DataType [ rowSize , colSize ];

DataType [ , ] arrName =

new DataType [ rowSize , colSize ];

int[,] M = new int[2, 2];

M [0, 0] = 1; M [0, 1] = 2;

M [1, 0] = 5; M [1, 1] = 3;

int[,] M = { {1,8} , {2,5} };

G etLength(int dim ension)

int[,] M = {{1,8},{2,5},{1,1} };

row = M G etLength(0); row = 3

col= M G etLength(1); col= 2

int[, ,] M 2 = new Int32[3, 4, 5];

for ( int i = 0; i < M G etLength(0); i+ + )

Arrays of Arrays

When we want to create a multi Array with

different size:

- The first, we declare size of row, so each

row will hold an array with any size

- The second, We will declare those array

- And Initialize value for each item in array

DataType[ ][ ] arrName = new DataType[Size][ ];

int [][] K = new int [3][];

Array Class

Provides methods for creating, manipulating, searching, and sorting arrays, thereby serving as the base class for all arrays in the common language runtime.

CreateInstance(Type, Int32 [])

Creates a multidimensional Array of the

specified Type and dimension lengths, with

zero-based indexing The dimension lengths

are specified in an array of 32-bit integers

// Creates and initializes a new tw

o-dim ensional Array of type Int32.

(2 row s, 3 cols)

Array m yArr =

Array C reateInstance( typeof ( Int32 ),2, 3);

i < = m yArr.G etU pperBound(0); i+ + )

j < = m yArr.G etU pperBound(1); j+ + )

{

m yArr.SetValue(i+ j, i, j);

}

for ( int i = m yArr.G etLow erBound(0);

i < = m yArr.G etU pperBound(0); i+ + )

{

for ( int j =

m yArr.G etLow erBound(1);

j < = m yArr.G etU pperBound(1); j+ + )

Method Description

Copy(Array,

Array, Int32) Copies a range of elements from an Array starting at the

first element and pastes them into another Array starting at the first element The length is specified as a 32-bit integer

int[] m yArr = new int[5] { 1, 2, 3, 4,

5 };

O bject[] m yO bjArr = new O bject[5]

{ 26, 27, 28, 29, 30 };

Copy 2 elem ent from m yArr to m yO bjArr:

Array.C opy(m yArr,m yO bjArr,2) ;

BinarySearch(Array, Object)

Searches an entire one-dimensional sorted Array

interface implemented by each element of the

Array and by the specified object ( not found =-1)

int[] M = new int[5] { 1, 2, 3,

4, 5 };

int found=Array.BinarySearch(M, 8);

Method Description

Sort(Array) Sorts the elements in an entire

one-dimensional Array using the IComparable

implementation of each element of the Array

int[] M 1 = new int[]{1,9,2,7,8};

Array.Sort(M 1);

O ut put: 1 2 7 8 9

ArrayList Class

using an array whose size is dynamically increased as required

Constructors Description

ArrayList () Initializes a new instance of

the ArrayList class that is empty and has the default initial capacity

A rrayList arrList = new

Constructors Description

ArrayList(Int32) Initializes a new instance

of the ArrayList class that

is empty and has the specified initial capacity

A rrayList arrList = new

(ICollection) Initializes a new instance of the ArrayList class that

contains elements copied from the specified collection and that has the same initial capacity as the number of

elements copied

A rrayList arr1= new A rrayList();

A rrayList arr2 = new A rrayList(arr1);

Method Description

Add Adds an object to the end of

the ArrayList

ArrayList arr= new ArrayList();

arr.Add(1);arr.Add( "a" );arr.Add( 9 );

foreach (object item in arr)

Console.W rite(item + “ ”);

//Output : 1 a 9

Method Description

AddRange Adds the elements of an

ICollection to the end of the ArrayList

A rrayList arr= new A rrayList();

foreach (int value in arr)

Console.W rite(value+ " ");

//Output : 1 1 4

Method Description

Insert Inserts an element into the

ArrayList at the specified index

A rrayList arr= new A rrayList();

foreach (object value in arr)

Console.W rite(value+ " ");

//Output : 1 teo 1 4

InsertRange Inserts the elements of a

collection into the ArrayList at the specified index

A rrayList arr= new A rrayList();

arr.AddRange( new int [] { 1, 1, 4 });

A rrayList arrIns= new A rrayList();

arrIns.Add( "teo" );

arrIns.Add( 9 );

foreach ( object value in arr)

Console W rite(value+ " " );

//Output : 1 1 teo 9 4

Remove Removes the first occurrence of a

specific object from the ArrayList

A rrayList arr= new A rrayList();

arr.AddRange(new object[]

Method Description

RemoveAt Removes the element at the

specified index of the ArrayList

A rrayList arr= new A rrayList();

arr.AddRange(new object[]

RemoveRange Removes a range of elements

from the ArrayList

A rrayList arr = new A rrayList();

arr.AddRange(new object[]

{ 1, "teo", 4, "ti" });

arr.Rem oveRange(1, 2);

//1 is Start Index to rem ove

//2 is num ber of elem ent to rem ove

foreach ( object value in arr)

Console W rite(value + " " );

//Output : 1 ti

Property Description

Count Gets the number of elements

actually contained in the ArrayList

A rrayList arr= new A rrayList();

arr.AddRange(new object[]

{ 1, "teo", 4, "ti" });

Console.W rite(arr.Count + " ");

//Output : 4

Method Description

Clear Removes all elements from the

ArrayList

A rrayList arr= new A rrayList();

arr.AddRange(new object[]

{ 1, "teo", 4, "ti" });

arr.C lear();

Console.W rite(arr.Count + " ");

//Output : 0

Contains Determines whether an element

is in the ArrayList

A rrayList arr = new A rrayList ();

"Pheo" , "Thi" , "N o" });

bool bFound = arr.C ontains("N o");

IndexOf Searches for the specified Object and

returns the zero-based index of the first occurrence within the entire

ArrayList

A rrayList arr = new A rrayList ();

arr.AddRange( new string [] { "Chi" , "Pheo" ,

"Thi" , "N o" });

int pos1 = arr.IndexO f("Pheo" );

Console W riteLine( "Pos1= " + pos1);

//Output : Pos1=1

int pos2 = arr.IndexO f(“Teo" );

Console W riteLine( "Pos2= " + pos2);

//Output : Pos2=-1

Method Description

LastIndexOf Searches for the specified Object

and returns the zero-based index

of the last occurrence within the entire ArrayList

A rrayList arr = new A rrayList ();

arr.AddRange(new string[] { “Teo",

"Pheo", "Thi", “Teo" });

int pos = arr.LastIndexO f(“Teo");

Console.W riteLine("Pos= "+ pos);

//Output : Pos=3

Sort Sorts the elements in the entire

BinarySearch Searches the entire sorted

ArrayList for an element using the default comparer and returns the zero-based index of the element

A rrayList arr = new A rrayList();

arr.Add(9);arr.Add(7);arr.Add(5);

arr.S ort();//M ust call Sort m ethod

int Found= arr.BinarySearch(9);

Console.W riteLine("Found= "+ Found);

//Output : Found=2

Clone Creates a shallow copy of the

ArrayList

A rrayList arr = new A rrayList();

arr.Add(9);arr.Add(7);arr.Add(5);

A rrayList arrN oC lone = arr;

arrN oClone.Rem oveAt(0);

foreach (object val in arr)

Console.W rite(val + " ");

//Output : 7 5

What’s happen when We use Clone method???

A rrayList arr = new A rrayList();

CopyTo Copies the entire ArrayList to a

compatible one-dimensional Array, starting at the beginning of the target array

A rrayList arr= new ArrayList ();

arr.Add(1);arr.Add( "a" );arr.Add( 9 );

object []M 1= new object [arr.Count];

arr.C opyTo(M 1);

foreach ( object val in M 1)

Console W rite(val + " " );

//Output : 1 a 9

A rrayList arr= new ArrayList ();

arr.Add(1);arr.Add( "a" );arr.Add( 9 );

foreach ( object val in M 1)

Console W rite(val + " " );

//Output : 9 a 1

Dictionary< TKey , TValue >

Represents a collection of keys and values

 Each addition to the

dictionary consists of a value and its associated key.

its key is very fast, close to O(1).

 Every key in a Dictionary

<TKey, TValue > must be

unique according to the

dictionary's equality comparer

 A key cannot be null , but a

value can be, if the value type

TValue is a reference type

 The capacity is automatically

increased as required by

reallocating the internal array

 Use KeyValuePair <TKey, TValue >

structure representing a value and its key.

Dictionary <TKey, TValue >()

Description:

Initializes a new instance of the

Dictionary <TKey, TValue > class

that is empty, has the default

initial capacity, and uses the

default equality comparer for the key type

// Create a new dictionary of

ArrayList, with string keys.

Dictionary < string , ArrayList >

Dictionary < string , ArrayList >();

// Or

Dictionary<string, ArrayList > myDIC = new

Dictionary<string, ArrayList >

(StringCom parer CurrentCultureIgnoreCase

);

Add ( TKey key, TValue value )

A rrayList aItem = m yD IC["H om e"];

foreach ( K eyValuePair< string,

A rrayList> item in m yD IC){

string strK ey = item Key;

A rrayList arrValue = item Value;

}

KeyValuePair <TKey, TValue>

Defines a key/value pair that can be set or

retrieved

public bool ContainsKey (TKey key)

Description:

Determines whether the

Dictionary <TKey,TValue>

contains the specified key

if (m yD IC.C ontainsK ey("H om e"))

{

M essageBox.Show (“Có hom e");

}

public bool ContainsValue

(TValue value )

Description:

Determines whether the

Dictionary <TKey, TValue>

contains a specific value

if (m yD IC.C ontainsValue(arr))

{M essageBox Show ( "Có Arr này rỗồ i" );

}

public bool TryGetValue

(TKey key, out TValue value )

Description:

Gets the value associated with the specified

key

A rrayList arr = null ;

if (m yD IC.TryG etValue( "H om e" , out arr))

{ //Process arr here

}

else { //Could not G et value

}

Count

Description:

Gets the number of key/value

pairs contained in the

Dictionary <TKey, TValue >

ArgumentNullException=>key is null

A rrayList aItem = m yD IC["H om e"];

m yD IC["H om e"]= arr (A rraylist);

Description:

Gets a collection containing the keys in the

Dictionary <TKey, TValue > Example:

D ictionary < string , A rrayList >

m yD IC.K eys;

foreach (string s in keyColl)

{//Process Key here

}

Description:

Gets a collection containing the values in the

Dictionary <TKey, TValue > Example:

D ictionary< string, A rrayList>

m yD IC.Values;

foreach(A rrayList arr in valColl)

{//Process value here

}

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