字符串和正则表达式

1.1. Creating Strings
1)
字符串字面值:

assign a quoted string of characters
string newString = "This is a string literal";
2)
原样输出
:start with the (@) symbol
Chapter 10 Strings
& Regular Expressions
1. 字符串

public sealed class String : IComparable<T>, ICloneable, IConvertible, IEnumerable<T> IComparable<T> ICloneable IConvertible IEnumerable<T>
// create some strings to work with string s1 = "abcd"; string s2 = "ABCD"; string s3 = @"Liberty Associates, Inc. // compare two strings, case sensitive provides custom .NET development, on-site pare( boolean // concatenation method result = Training and takess1, s2 // overloaded compare,Consulting"; ); "ignore case" s6 = string.Concat( s1, string //(true = ignore case) ); Console.WriteLine( s2 int result; // hold Console.WriteLine(the results of comparisons "compare s1: {0}, s2: {1}, result: {2}\n", result = pare( s1, s2, true ); "s6 concatenated from s1 and s2: {0}", s6 ); s1, s2, result ); Console.WriteLine( "compare insensitive\n" ); // use the overloaded operator string Console.WriteLine( "s4: {0}, s2: {1}, result: s7 = s1 + s2; {2}\n", Console.WriteLine( "s7 concatenated from s1 + s2: {0}", s7 ); s1, s2, result );


String类的缺点

String类的效率低，不够灵活。
StringBuilder类可弥补String类的不足。

1.6. 操作动态字符串

System.Text.StringBuilder类用于创建和修饰 字符串。
和String类相比，StringBuilder类是可变的， 当你修改字符串对象时，修改的是实际的字符 串，而不是string类的副本。
1.5. 分离字符串

The job of Split( ) method is to parse(从语法书分析) a string into substrings. char[ ] delimiters = new char[ ] { Space, Comma }; string output = ""; int ctr = 1; // split the string and then iterate over the // resulting array of strings foreach ( string subString in s1.Split( delimiters ) ) { output += ctr++; output += ": "; output += subString; output += "\n"; } Console.WriteLine( output );







// the string copy method string s8 = string.Copy( s7 ); Console.WriteLine( // three ways to compare. Clone方法两个字符串指向内 "s8 copied from s7: {0}", s8 ); Console.WriteLine( 存中的同一个字符串 // use the overloaded {0}", operator "\nDoes s9.Equals(s8)?: // Two useful properties: the index and the length string s9 = s8; s9.Equals( s8 ) ); Console.WriteLine( Console.WriteLine( "s9 = s8: {0}", s9 ); Console.WriteLine(


string literalOne = "\\\\MySystem\\MyDirectory\\ProgrammingC#.cs";
string verbatimLiteralOne = @"\\MySystem\MyDirectory\ProgrammingC#.cs";

string literalTwo = "Line One\nLine Two"; string verbatimLiteralTwo = @"Line One Line Two";
2. 正则表达式

正则表达式是对字符串描述和操作的强大语言， 通常这样的字符串是一个整个文档。
正则表达式可以：


来发现符合正则表达式的字符串匹配 返回一个子串 返回一个代表原字符串某些部分修改内容的新字符 串

正则表达式通常包含两种字符:



// return the index of the substring Console.WriteLine( "\nThe first occurrence of Training " ); Console.WriteLine( "in s3 is {0}\n", s3.IndexOf( "Training" ) ); // insert the word excellent before "training" string s10 = s3.Insert( 101, "excellent " ); Console.WriteLine( "s10: {0}\n", s10 ); // you can combine the two as follows: string s11 = s3.Insert( s3.IndexOf( "Training" ), "excellent " ); Console.WriteLine( "s11: {0}\n", s11 );



StringBuilder output = new StringBuilder( ); int ctr = 1; ………………… foreach ( string subString in s1.Split( delimiters ) ) { // AppendFormat appends a formatted string output.AppendFormat( "{0}: {1}\n", ctr++, subString ); } Console.WriteLine( output ); ………………………

用同样的值创建两个字符串


// test whether a is {0} characters a set of characters "\nString s9 string ends with long. ", "Does Equals(s9,s8)?: {0}", Console.WriteLine( "s3:{0}\nEnds with Training?: 三种方式来比较两个字符串相 s9.Length ); string.Equals( s9, s8 ) ); {1}\n", 等性 Console.WriteLine( Console.WriteLine( s3, "The 5th character s9 {1}\n", ); "Does s9==s8?: {0}", is == s8 s3.EndsWith( "Training" ) ); s9.Length, s9[4] ); Console.WriteLine( "Ends with Consulting?: {0}", s3.EndsWith( "Consulting" ) );