Bài giảng Lập trình C# 2010: Chương 6 - ĐH Đồng Nai Công nghệ Đồng Nai

DONG NAI UNIVERSITY OF TECHNOLOGY


DONG NAI UNIVERSITY OF TECHNOLOGY

String Class
Represents text as a series of Unicode
characters.


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Constructor
There are many overload Constructors. I would like to tell you the
Constructor below:

String Constructor ( Char [])
Initializes a new instance of the String class to the value indicated by
an array of Unicode characters.


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Constructor
strin g strH U I= new strin g
(new char[]{'H ','U ','I'});
M essageBox.Show (strH U I);
Use string or S trin g ?
S trin g strH U I= new S trin g
(new char[]{'H ','U ','I'});
M essageBox.Show (strH U I);

DONG NAI UNIVERSITY OF TECHNOLOGY

String Fields
Empty
Represents the empty string. This field is readonly.
string strName = string.Empty;


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String Operators
Name

Description

Equality(==)

Determines whether two specified

“a”==“A”?false

strings have the same value.

“a”==“a”?true
Inequality(!=)

Determines whether two specified

“a”!=“A”?true

strings have different values.

“a”!=“a”?false


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String Properties
Name

Description

Chars

Gets the character at a specified character
position in the current String object.

char ch = strHUI[0];
Length

Gets the number of characters in the
current String object.

int nSize = strHUI.Length;


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String Methods
Name
public static int Compare
( string strA, string strB )
Description
Compares two specified String objects and returns an integer that
indicates their relative position in the sort order
0 strA equals strB
1 strA is greater than strB
-1 strA is less than strB


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String Methods
Example
int nRet = string.Compare(“A", “a");
nRet=1

int nRet = string.Compare(“a", “A");
nRet=-1

int nRet = string.Compare(“a", “a");
nRet=0


DONG NAI UNIVERSITY OF TECHNOLOGY

String Methods
Name

public static int Compare(
string strA, string strB,
bool ignoreCase )
Description
Compares two specified String objects ,ignoring or honoring their
case, and returns an integer that indicates their relative position in
the sort order


DONG NAI UNIVERSITY OF TECHNOLOGY

String Methods
Example
int nRet = string.Compare
(“A", “a”,true);nRet=0

int nRet = string.Compare
(“a", “A”,false);nRet=-1

int nRet = string.Compare
(“A", “a”,false);nRet=1


DONG NAI UNIVERSITY OF TECHNOLOGY

String Methods
Name
public int CompareTo( string strB )
Description
Compares this instance with a specified String object and indicates

whether this instance precedes, follows, or appears in the same
position in the sort order as the specified String. (0

;1 ;

-1)


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String Methods
Example
string strA = “A”;
string strB = “B”;
int nRet = strA.CompareTo(strB);
nRet=-1
string strA = “A”;
string strB = null;
int nRet = strA.CompareTo(strB);
nRet=1


DONG NAI UNIVERSITY OF TECHNOLOGY

String Methods
Name
public static string Copy(string str)
Description
Creates a new instance of String with the same value as a
specified String.

string str = string.Copy("Teo");
string str1 = "Ti";
string str2 =string.Copy(str1);


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String Methods
Name
public bool Contains( string value )
Description
Returns a value indicating whether the specified String object
occurs within this string

Return true or false


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String Methods
Example
string strA = "Trần Văn Tèo";
string strB = "Văn";
bool bRet = strA.Contains(strB);
if (!bRet)
MessageBox.Show("Khơng có
["+strB+"] trong ["+strA+"]");
else
MessageBox.Show("Có [" + strB + "]

trong [" + strA + "]");


DONG NAI UNIVERSITY OF TECHNOLOGY

String Methods
Name
public bool EndsWith( string value )
Description
Determines whether the end of this string instance matches the
specified string

Return true or false


DONG NAI UNIVERSITY OF TECHNOLOGY

String Methods
Example
string strA = "<div>Tèo </div>";
string strB = "</div>";
bool bRet = strA.EndsWith(strB);
if (bRet)
MessageBox.Show("có [" +
strB+"] ở cuối chuỗi");
else
MessageBox.Show("Ko có [" +

strB + "] ở cuối chuỗi");

DONG NAI UNIVERSITY OF TECHNOLOGY

String Methods
Name
public bool EndsWith( string value, StringComparison
comparType )
Description
Determines whether the end of this string instance matches the
specified string when compared using the specified comparison
option


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String Methods
Example
string strA = "<div><div>Tèo</div></div>";
string strB = "</DiV>";
bool bRet = strA.EndsWith(strB,
StringComparison.OrdinalIgnoreCase);
if (bRet)
MessageBox.Show("có [" + strB+"] ở

cuối

chuỗi");

MessageBox.Show("Ko có [" + strB +

"] ở cuối chuỗi");

else


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String Methods
Name
public static string Format
(string format, params Object[] args )

Description
Replaces the format item in a specified string with the string
representation of a corresponding object in a specified array


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String Methods
Example
string strFormat;
strFormat = string.Format("Tỉ giá {0:d} = {1:c}", DateTime.Today,
22.3);
MessageBox.Show(strFormat);


HO CHI MINH UNIVERSITY OF INDUSTRY

Author: Duy Thanh Tran – Phone : 0987773061- Email: – Blog:


DONG NAI UNIVERSITY OF TECHNOLOGY

String Methods
Name
public int IndexOf( char value )
Description
Reports the index of the first occurrence of the specified Unicode
character in this string.
The zero-based index position of value if that character is found,
or -1 if it is not


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String Methods
Example
string str = "N guyễễ
n ThịLong Lanh C hòng C hành Ánh Tuyễế
t";

int nRet= str.IndexO f('T');
nRet= 7

int nRet= str.IndexO f(‘t');
nRet= 41

int nRet= str.IndexO f(‘Ă');

nRet= -1