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

DONG NAI UNIVERSITY OF TECHNOLOGY


DONG NAI UNIVERSITY OF TECHNOLOGY

1

One Dimension Array

2

Multi Dimension Array

3

Array class

4

ArrayList class

5

Dictionary class


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One Dimension Array
M[0]

5

M[1]

M[2]

M[3]

M[4]

M[5]

M[6]

2

9

7

6

0

8

- Same name
- Same type
- Get Element by Index ( 0 n-1)

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Declaring & Creating Arrays
• 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


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Declaring:
Creating:

<DataType> [ ] <ArrayName>;
int [ ] M;
Button[ ] arrButton;

<ArrayName> =new <DataType>[ ARRAY_SIZE];
M=new int[10];
Button []arrButton=new Button[10];


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Examples…
int M1[]=new int[10];
for(int i=0;iM1[i]=i*2;
for(int i=0;iConsole.Write(M1[i] + “”);
foreach(int value in M1)
Console.Write(value + “”);
int M2[]={1,4,2} ;


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Properties & Methods

• array_name.Length: return size of array
• array_name.GetValue (int index): return an
object at position index.
• array_name[int index]: return an object at
position index.
• array_name.SetValue (object value, int index):
add or modify an object at position index
• array_name[int index] = value: add or modify an
object at position index


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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


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Passing Arrays to Method
static void in p u tA rray(int[] arr)
{
Random ran = new Random ();
for (int i= 0; i< arr.Length; i+ + )

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


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Using out or ref keyword to pass by reference
static void ed it(ou t in t n )
{
n = -113;
}

OR:

static void ed it(ref in t n )
{
n = -113;
}


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The out parameter must be assigned to
before control leaves the current method
static void edit(out int n)
{
//n = -113;
}
 Compile error


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arr[0]= 100;
U se ou t keyw ord :
ed it(ou t arr[0]);
U se ref keyw ord :
ed it(ref arr[0]);
Tw o w ays: arr[0] -113


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7

9
8

2 9 0
5 4 1
0 3 6
Multi
Dimension


Column 0
Row 0

Row 1

Row 2

Column 1

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Column 2

Column 3

M[0, 0]

M[0, 1]

M[0, 2]

M[0, 3]

7

2

9

0

M[1, 0]

M[1, 1]

M[1, 2]

M[1, 3]

9

5

4

1

M[2, 0]

M[2, 1]

M[2, 2]

M[2, 3]

8

0

3

6

Column index (or subscript)
Row index (or subscript)
Array name


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DataType[ , ] arrName;
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} };

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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];
x= M 2.G etLength(0);x=
3
y= M 2.G etLength(1);y=
4
z= M 2.G etLength(2);z=


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Examples
for (in t i = 0; i < M .G etLen g th (0); i+ + )

{
for (in t j = 0; j < M .G etLen g th (1); j+ + )

{
C on sole.W rite(M [i,j] + " ");
}
C on sole.W riteLin e();
}

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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][ ];


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int[][] K = new int[3][];
K[0] = new int[] { 1,3};
K[1] = new int[] { 9};
K[2] = new int[] { 5, 4,9 };
for (int i= 0; i< K.G etLength(0); i+ + )
{
for (int j= 0; j< K[i].Length; j+ + )
{
Console.W rite(K[i][j] + " ");
}
Console.W riteLine();
}


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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.


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Method
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.


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// Creates and initializes a new tw odim ensionalArray of type Int32.
(2 row s, 3 cols)
Array m yArr =
Array.C reateIn stan ce(typeof(Int32),2, 3);

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+ + )
{

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


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TO get value foreach item :
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+ + )
{
Console.W rite(
m yArr.G etV alu e(i, j) + " ");
}
Console.W riteLine();
}


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Method
Description
Copy(Array, Copies a range of elements
Array, Int32) 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


DONG NAI UNIVERSITY OF TECHNOLOGY

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 op y(m yArr,m yO bjArr,2) ;