Chapter :

1. Chapter : STRING

2. 1. Introduction • String and character processing capabilities • Text editors • Word processors… • Expand from previous chapters • Class String and type char • Class StringBuilder

3. Fundamentals of Characters and Strings • Importance of characters • Character constants • Character code • Unicode character set • String • Object of class String in System namespace • Consist of characters

4. String Constructors • Class String • Provides eight constructors for initialing strings string file = "C:\\MyFolder\\MySubFolder\\MyFile.txt"; string file = @"C:\MyFolder\MySubFolder\MyFile.txt";

5. Introduction • String and character processing capabilities • Text editors • Word processors… • Expand from previous chapters • Class String and type Char (System namespace) • Class StringBuilder (System.Text namespace)

6. String class: Initialing strings Using constructors of String class: new String (char[ ] chuoi_ki_tu); new String (char[ ] chuoi_ki_tu, int vi_tri_bat_dau_lay, int so_ki_tu); new String (char ki_tu, int so_lan_lap);

7. string output; string originalString, string1, string2, string3, string4; char[] characterArray = { 'b', 'i', 'r', 't', 'h', ' ', 'd', 'a', 'y' }; // string initialization originalString = "Welcome to C# programming!"; string1 = originalString; string2 = newstring( characterArray ); string3 = newstring( characterArray, 6, 3 ); string4 = newstring( 'C', 5 ); output = "string1 = " + "\"" + string1 + "\"\n" + "string2 = " + "\"" + string2 + "\"\n" + "string3 = " + "\"" + string3 + "\"\n" + "string4 = " + "\"" + string4 + "\"\n";

8. StringConstructor.cs

9. String Length Property and CopyTo Method • Length property • Returns the length of the string • CopyTo • Copies specified number of characters into a char array CopyTo ( intsourceIndex, array[] destination, intdestinationIndex, intcount ) Copy To: tại 1 ví trí trên chuỗi gốc (sourceIndex, ), lấy một số ký tự (count), Copy tới một vị trí (destinationIndex) , trên một bảng dãy ký tự Unicode destination;

10. StringMethods string string1, output; char[ ] characterArray; string1 = "hello there"; characterArray = newchar[ 10 ]; string1.CopyTo( 0, characterArray, 2, 5 ); output += "\nThe character array is: "; for ( int i = 0 ; i < characterArray.Length; i++ ) output += characterArray[ i ];

11. Comparing Strings • String comparison • Greater than (1) • Less than (-1) • Equal (0) • Method Equals • Test objects for equality • Return a Boolean • Uses lexicographical comparison

12. Comparing Strings • Method Equals: test objects for equality • Return a bool value: true if equal • boolString.Equals (String s1, String s2) • bool objectString.Equals (String s) • Method CompareTo: greater than, less than • Return a int value: • intString.Compare (String s1, String s2) • intString.Compare (String s1, String s2, bool ignoreCase) • int objectString.CompareTo (String s)

13. Comparing Strings • String s1, s2; • S1= ; • S2= ; • S1.CompareTo(s2) car Car hi Return -1: S1 < S2 Return 1: S1 > S2 Return -1: S1 < S2 hello Car Cat

14. Locating Characters in Strings • IndexOf methods: Reports the index of the first occurrence of a String, or one or more characters, within this string. • IndexOf(char value) • IndexOf(char value, int StartIndex) • IndexOf(string value) • IndexOf(string value, int StartIndex) • ;

15. Locating Characters in Strings IndexOfAny method: report the first occurrence int objectString.IndexOfAny (char[] value) int objectString.IndexOfAny (char[] value, int startIndex)

16. Locating Characters in Strings • LastIndexOf method: report the last occurence • int objectString.LastIndexOf (string value) • int objectString.LastIndexOf (string value, int startIndex) • int objectString.LastIndexOf (string value, int startIndex, int limit) • int objectString.LastIndexOf (char value) • int objectString.LastIndexOf (char value, int startIndex) • LastIndexOfAny method: report the last occurrence • int objectString.LastIndexOf (char[] value) • int objectString.LastIndexOf (char[] value, int startIndex)

17. Working With String • Bool MyString.StartsWith( s ) • Bool MyString.EndsWith( s ) • string MyString.Substring ( intstartIndex, intlength ) • MyString.ToLower( ) • MyString.ToUpper( ) • MyString.ToString( ) • MyString.Trim( ) • MyString.TrimEnd( ) • MyString.TrimStart ( )

18. StartsWith(strA) strA=“Working with String” strB=“w” strA.StartsWith("T") = F strA.StartsWith(strB) = F strA.StartsWith(strB.ToUpper) = T

19. Example • strA=“Working with String” • strB = "w“ strA.IndexOf("w") = 8 strA.IndexOf(strB.ToUpper) = 0 strA.IndexOf(strB.ToUpper, 3) = -1 strA.IndexOf(“ “, 3) = 7

20. Example • strA=“Working with String” • strB = "w“ strA.Substring(8) = with String strA.Substring(8, 4) = with strA.Substring(strA.IndexOf("S")) = String

21. Replace String Methods • Method Replace (phương thức thay thế chuỗi) • Original string remain unchanged • String objectString.Replace (String oldValue, String newValue) • String objectString.Replace (char oldValue, char newValue)

22. Tách chuỗi • Sử dụng phương thức Split() của lớp String: phân tích một chuỗi ra thành các chuỗi con dựa vào ký tự phân cách. • Cú pháp: Split (char[] sign), hàm trả về một mảng chuỗi • Để sử dụng Split(), chúng ta truyền vào một mảng các ký tự phân cách, các ký tự này được dùng để chia các từ trong chuỗi. • Ví dụ: Tách chuỗi “Nguyễn Văn An” dựa vào khoảng trắng.

23. Ví dụ string s1 = “Nguyễn Văn An"; char[ ] space = {' '}; string[ ] s; s = s1.Split (space); //tham so truyen la mang ky tu txtHo.Text = s[0]; txtTen.Text = s[s.Length - 1]; for ( int i=1; i<s.Length-2; i++) { txtHolot.Text += s[i] + “ “; }

24. Finish