学用 ASP.Net 之 "字符串" (4): string 类的扩展方法

学到这里, 真是开眼界了...有太多陌生的概念.
string 类的扩展方法大都继承自 IEnumerable<T> 接口, 这些方法也大都可以在 foreach 语句中实现, 但这些方法太方便了.
尽管 string 类重载了其中很多方法, 但真正适合字符串操作的方法并不多; 此时我感觉, 前两天定下的学习计划出了问题, 因为仅用字符串很难理清这组方法; 不过要继续...

string 类的扩展方法列表(基本相同于 IEnumerable<T> 接口的成员列表):

Aggregate<>          //累加All<>                //是否都满足条件Any<>                //是否有一个满足条件AsEnumerable<>       //AsParallel<>         //AsQueryable<>        //Average<>            //平均值Cast<>               //Concat<>             //连接Contains<>           //是否包含Count<>              //总数DefaultIfEmpty<>     //指定默认空值Distinct<>           //去除重复ElementAt<>          //获取指定位置的元素ElementAtOrDefault<> //同 ElementAt, 但获取失败则返回默认的空值Except<>             //差集First<>              //获取第一个元素FirstOrDefault<>     //同 First, 但获取失败返回默认的空值GroupBy<>            //分组GroupJoin<>          //关联分组Intersect<>          //交集Join<>               //串联Last<>               //获取最后一个元素LastOrDefault<>      //同 Last, 但获取失败返回默认的空值LongCount<>          //同 Count, 但返回 Int64Max<>                //最大值Min<>                //最小值OfType<>             //OrderBy<>            //排序OrderByDescending<>  //倒排序Reverse<>            //翻转Select<>             //映射SelectMany<>         //深度映射SequenceEqual<>      //Single<>             //获取只是唯一的元素, 不唯一或获取不到则异常SingleOrDefault<>    //获取只是唯一的元素, 不唯一则异常, 获取不到则取默认空值Skip<>               //获取指定序号之后的SkipWhile<>          //获取指定条件之后的Sum<>                //求和Take<>               //获取指定序号之前的TakeWhile<>          //获取指定条件之前的ToArray<>            //ToCharArray<>        //ToDictionary<>       //ToList<>             //ToLookup<>           //Union<>              //并集Where<>              //筛选Zip<>                //合并

获取首尾的字符(First、Last、FirstOrDefault、LastOrDefault):

/* 函数及重载 */First <Char>()                               // 函数名: First; <Char> 中的 Char 是返回值类型; () 表示这是一个无参数的重载First <Char> (Func <Char, Boolean>)          // 这里的参数是个函数, 其(函参)返回值是 Boolean 类型, 参数是 Char 类型.                                             // <> 中是函数参数与返回值的列表, 最后一个是返回值.FirstOrDefault <Char>()                      // 同 First, 但如果找不到则返回默认值 nullFirstOrDefault <Char> (Func <Char, Boolean>) //Last <Char>()                                // 顾名思义, 同上Last <Char> (Func <Char, Boolean>)           //LastOrDefault <Char>()                       //LastOrDefault <Char> (Func <Char, Boolean>)  ////下面例子很容易理解:protected void Button1_Click(object sender, EventArgs e){    string str = "ABCDEFG";    char c1 = str.First(); // A    char c2 = str.Last();  // G    TextBox1.Text = string.Concat(c1, "\n", c2);}//下面例子使用了其第二种重载, 其参数是个函数, 使用了 Lambda 匿名函数表达式:protected void Button2_Click(object sender, EventArgs e){    string str = "ABCDEFG";    char c1 = str.First(p => p != 'A'); // B : 这是获取不是 A 的第一个字符    char c2 = str.Last(p => p < 70);    // E : 这是获取字符编码值大于 70(F) 的倒数第一个字符    TextBox1.Text = string.Concat(c1, "\n", c2);}// Lambda 表达式中, // => 前面的是参数列表, 其类型可被自动识别所以可省略, 只有一个参数时可省略括号; 其中的 p 是自定义的变量名.// => 后面的是函数内容, 通常只有一句话; 但其必须返回指定的类型(本例中是 Boolean).//测试用于其它数组:protected void Button3_Click(object sender, EventArgs e){    int[] nArr = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };    string[] sArr = { "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten" };    int n1 = nArr.First();                     //1    int n2 = nArr.First(x => x % 2 == 0);      //2    string s1 = sArr.Last();                   //ten    string s2 = sArr.Last(s => s.Length == 5); //eight    TextBox1.Text = string.Concat(n1, "\n", n2, "\n", s1, "\n", s2);}

获取指定位置的元素(ElementAt、ElementAtOrDefault):

protected void Button1_Click(object sender, EventArgs e){    string str = "Asp.Net 4.0";    char c1 = str.ElementAt(1);            //s    char c2 = str.ElementAtOrDefault(1);   //s    char c3 = str.ElementAtOrDefault(999); //    bool b1 = c3 == '\x00';                //True    TextBox1.Text = string.Concat(c1, "\n", c2, "\n", c3, "\n", b1);}

统计操作(Aggregate、Count、LongCount、Max、Min、Sum、Average):

//用数字数组测试比较合适protected void Button1_Click(object sender, EventArgs e){    int[] nArr = { 2, 1, 4, 3, 6, 5 };    int n1 = nArr.Count();                    //6     int n2 = nArr.Count(n => n % 2 == 0);     //3 : 偶数元素总数    int n3 = nArr.Sum();                      //21    int n4 = nArr.Max();                      //6    int n5 = nArr.Min();                      //1    double n6 = nArr.Average();               //3.5    int n7 = nArr.Aggregate((x, y) => x * y); //720 : 累乘    Int64 n8 = nArr.LongCount();              //6 : LongCount 和 Count 只是返回值的类型不同    string r = "\n";    TextBox1.Text = string.Concat(n1 + r + n2 + r + n3 + r + n4 + r + n5 + r + n6 + r + n7 + r + n8);}protected void Button2_Click(object sender, EventArgs e){    string str = "one two three four five six seven eight nine ten";    int n1 = str.Count();              //48 : 这相当于 str.Length    int n2 = str.Count(s => s != ' '); //39 : 这是非空格字符的总数    char c1 = str.Max();               //x  : 这是序号最大的字符    char c2 = str.Min();               //序号最小的字符在这里是空格    TextBox1.Text = string.Concat(n1, "\n", n2, "\n", c1, "\n", c2);}//通过 Aggregate 翻转字符串中的单词protected void Button3_Click(object sender, EventArgs e){    string str = "one two three four five six seven eight nine ten";    string[] sArr = str.Split(' ');    str = sArr.Aggregate((s1, s2) => s2 + " " + s1); //ten nine eight seven six five four three two one    TextBox1.Text = str;}

集合操作(Intersect、Except、Union):

//测试整数数组的交集、差集、并集protected void Button1_Click(object sender, EventArgs e){    int[] nArr1 = { 1, 2, 3, 4, 5, 6 };    int[] nArr2 = { 4, 5, 6, 7, 8, 9 };    IEnumerable<int> R1 = nArr1.Intersect(nArr2); // 返回类型可以写作隐式类型 var    var R2 = nArr1.Except(nArr2);    var R3 = nArr1.Union(nArr2);    string s1 = string.Join("", R1); //456    string s2 = string.Join("", R2); //123    string s3 = string.Join("", R3); //123456789    TextBox1.Text = string.Concat(s1, "\n", s2, "\n", s3);}//测试字符串(字符数组)的交集、差集、并集protected void Button2_Click(object sender, EventArgs e){    string str1 = "Asp.Net 3.5";    string str2 = "ASP.NET 4.0";    var R1 = str1.Intersect(str2);    var R2 = str1.Except(str2);    IEnumerable<char> R3 = str1.Union(str2);    string s1 = string.Join("", R1); //A.N     string s2 = string.Join("", R2); //spet35    string s3 = string.Join("", R3); //Asp.Net 35SPET40    TextBox1.Text = string.Concat(s1, "\n", s2, "\n", s3);}//定义一个 Person 类, 其有 Name 和 Age 两个属性public class Person{    public string Name { get; set; }    public int Age { get; set; }    public Person(string name, int age) { Name = name; Age = age; } // 构造函数}//自定义的对比类, 以比较是否是同一个人public class PersonComparer : IEqualityComparer<Person>{    public bool Equals(Person p1, Person p2)    {        return p1.Name == p2.Name && p1.Age == p2.Age;    }    public int GetHashCode(Person obj)    {        return 0;    }}//获取两组人的交集、差集、并集protected void Button3_Click(object sender, EventArgs e){    string s1, s2, s3;    s1 = s2 = s3 = "";    Person[] PersonArr1 = { new Person("AA", 11), new Person("BB", 22), new Person("CC", 33) };    Person[] PersonArr2 = { new Person("CC", 33), new Person("DD", 44), new Person("AA", 55) };    var ps1 = PersonArr1.Intersect(PersonArr2, new PersonComparer());    var ps2 = PersonArr1.Except(PersonArr2, new PersonComparer());    IEnumerable<Person> ps3 = PersonArr1.Union(PersonArr2, new PersonComparer());    foreach (Person p in ps1) { s1 += string.Format("{0}:{1} ", p.Name, p.Age); } //CC:33     foreach (Person p in ps2) { s2 += string.Format("{0}:{1} ", p.Name, p.Age); } //AA:11 BB:22     foreach (Person p in ps3) { s3 += string.Format("{0}:{1} ", p.Name, p.Age); } //AA:11 BB:22 CC:33 DD:44 AA:55    TextBox1.Text = string.Concat(s1, "\n", s2, "\n", s3);}

连接、合并与串联(Concat、Zip、Join):

//Concatprotected void Button1_Click(object sender, EventArgs e){    int[] nArr1 = { 1, 2, 3 };    int[] nArr2 = { 4, 5, 6 };    var R1 = nArr1.Concat(nArr2);    var R2 = nArr2.Concat(nArr1);    var R3 = nArr1.Concat(nArr1);    string s1 = string.Join("", R1); //123456    string s2 = string.Join("", R2); //456123    string s3 = string.Join("", R3); //123123    TextBox1.Text = string.Format("{0}\n{1}\n{2}", s1, s2, s3);}//Zipprotected void Button2_Click(object sender, EventArgs e){    string[] sArr = { "one", "two", "there" };    int[] nArr = { 1, 2, 3 };    var R1 = sArr.Zip(nArr, (x1, x2) => x1 + ":" + x2 + " ");    var R2 = sArr.Zip(nArr, (x1, x2) => x2 + ":" + x1 + " ");    string s1 = string.Join("", R1); //one:1 two:2 there:3     string s2 = string.Join("", R2); //1:one 2:two 3:there     TextBox1.Text = string.Concat(s1, "\n", s2);}//Joinprotected void Button3_Click(object sender, EventArgs e){    int[] nArr = { 1, 2, 3, 4, 5, 6, 7 };    string[] sArr = { "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten" };    var R = nArr.Join(sArr, n => n, s => s.Length, (n, s) => new { n, s });    string str = "";    foreach (var obj in R)    {        str += obj.n + " : " + obj.s + "\n";    }    TextBox1.Text = str;/* 输出结果:    3 : one    3 : two    3 : six    3 : ten    4 : four    4 : five    4 : nine    5 : three    5 : seven    5 : eight*/}

去除重复(Distinct):

protected void Button1_Click(object sender, EventArgs e){    string str = "aabbccc";    var cs = str.Distinct();    foreach (char c in cs) { TextBox1.Text += c; } //abc}protected void Button2_Click(object sender, EventArgs e){    int[] nArr = { 1, 3, 2, 4, 3, 5, 4, 6, 5, 7, 6, 8, 7, 9, 8, 0 };    var ns = nArr.Distinct().OrderBy(x => -x);    foreach (int n in ns) { TextBox1.Text += n.ToString(); } //9876543210}

排序(OrderBy、OrderByDescending):

protected void Button1_Click(object sender, EventArgs e){    int[] nArr = { 1, 3, 2, 4, 3, 5 };    string[] sArr = { "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten" };    string str = "Asp.Net";    var R1 = nArr.OrderBy(x => x);    var R2 = nArr.OrderByDescending(x => x);    var R3 = sArr.OrderBy(x => x);    var R4 = sArr.OrderByDescending(x => x);    var R5 = str.OrderBy(x => x.ToString().ToLower());    var R6 = str.OrderByDescending(x => x.ToString().ToLower());    string s1 = string.Join("", R1);  //123345    string s2 = string.Join("", R2);  //543321    string s3 = string.Join(" ", R3); //eight five four nine one seven six ten three two     string s4 = string.Join(" ", R4); //two three ten six seven one nine four five eight     string s5 = string.Join("", R5);  //.AeNpst    string s6 = string.Join("", R6);  //tspNeA.     TextBox1.Text = string.Concat(s1, "\n", s2, "\n", s3, "\n", s4, "\n", s5, "\n", s6);}

翻转(Reverse):

protected void Button1_Click(object sender, EventArgs e){    string str = "Asp.Net";    var cs = str.Reverse();    foreach (char c in cs) { TextBox1.Text += c; } //teN.psA}

筛选(Where):

protected void Button1_Click(object sender, EventArgs e){    int[] nArr = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };    string[] sArr = { "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten" };    var R1 = nArr.Where(n => n % 2 == 0);    var R2 = sArr.Where(s => s.Length == 3);    string s1 = string.Join(", ", R1); //2, 4, 6, 8    string s2 = string.Join(", ", R2); //one, two, six, ten    TextBox1.Text = string.Concat(s1, "\n", s2);}

映射(Select、SelectMany):

//Selectprotected void Button1_Click(object sender, EventArgs e){    int[] nArr = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };    string[] sArr = { "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten" };    var R1 = nArr.Select(n => n * n);    var R2 = sArr.Select((str, index) => (index+1) + ":" + str.ToUpper());    string s1 = string.Join(",", R1); //1,4,9,16,25,36,49,64,81    string s2 = string.Join(" ", R2); //1:ONE 2:TWO 3:THREE 4:FOUR 5:FIVE 6:SIX 7:SEVEN 8:EIGHT 9:NINE 10:TEN    TextBox1.Text = string.Concat(s1, "\n", s2);}//Select 与 SelectManyprotected void Button2_Click(object sender, EventArgs e){    string[] sArr = { "AA:BB:CC", "DD:EE:FF", "GG:HH:II" };    var R1 = sArr.Select(arr => arr.Split(':'));    var R2 = sArr.SelectMany(arr => arr.Split(':'));    var s1 = string.Join(" ", R1); //System.String[] System.String[] System.String[]    var s2 = string.Join(" ", R2); //AA BB CC DD EE FF GG HH II    var s3 = "";    foreach (string[] ss in R1) { s3 += string.Join(" ", ss) + "; "; } //AA BB CC; DD EE FF; GG HH II;     TextBox1.Text = string.Concat(s1, "\n", s2 + "\n" + s3);}

分组(GroupBy、GroupJoin):

public class Person{    public string Name { get; set; }    public int Age { get; set; }}protected void Button1_Click(object sender, EventArgs e){    Person[] pArr =     {        new Person { Name="AA", Age=11 },        new Person { Name="BB", Age=22 },        new Person { Name="CC", Age=33 },        new Person { Name="DD", Age=11 },        new Person { Name="EE", Age=22 },        new Person { Name="FF", Age=33 },        new Person { Name="GG", Age=11 }    };    var R1 = pArr.GroupBy(p => p.Age, p => p.Name);    var R2 = pArr.GroupBy(p => p.Age, p => p);    string str1 = "";    foreach (IGrouping<int, string> group in R1)    {        str1 += group.Key + "\n";        foreach (string n in group) {             str1 += "\t" + n + "\n";         }    }    string str2 = "";    foreach (IGrouping<int, Person> group in R2)    {        str2 += group.Key + "\n";        foreach (Person p in group)        {            str2 += string.Format("\t{0}:{1}\n", p.Name, p.Age);        }    }    TextBox1.Text = string.Format("{0}----------\n{1}", str1, str2);/* 输出结果:11AADDGG22BBEE33CCFF----------11AA:11DD:11GG:1122BB:22EE:2233CC:33FF:33*/}//使用 GroupJoin, 测试效果同上protected void Button1_Click(object sender, EventArgs e){    int[] nArr = { 11, 22, 33 };     Person[] pArr =     {        new Person { Name="AA", Age=11 },        new Person { Name="BB", Age=22 },        new Person { Name="CC", Age=33 },        new Person { Name="DD", Age=11 },        new Person { Name="EE", Age=22 },        new Person { Name="FF", Age=33 },        new Person { Name="GG", Age=11 }    };    var R1 = nArr.GroupJoin(pArr, n => n, p => p.Age, (n, ps) => new { MyKey = n, MyNames = ps.Select(p => p.Name) });    var R2 = nArr.GroupJoin(pArr, n => n, p => p.Age, (n, ps) => new { MyKey = n, MyNames = ps });    string str1 = "";    foreach (var obj in R1)    {        str1 += obj.MyKey + "\n";        foreach (string s in obj.MyNames)        {            str1 += string.Format("\t{0}\n", s);        }    }    string str2 = "";    foreach (var obj in R2)    {        str2 += obj.MyKey + "\n";        foreach (var p in obj.MyNames)        {            str2 += string.Format("\t{0}:{1}\n", p.Name, p.Age);        }    }    TextBox1.Text = string.Format("{0}----------\n{1}", str1, str2);}

获取指定条件之后的(Skip、SkipWhile)或之前的(Take、TakeWhile):

//Skip、SkipWhileprotected void Button1_Click(object sender, EventArgs e){    int[] nArr = { 1, 3, 2, 4, 3, 5 };    var R1 = nArr.Skip(3);                           //取第 3 个元素之后的    var R2 = nArr.OrderBy(n => n).Skip(3);           //先排序, 再取第 3 个元素之后的    var R3 = nArr.OrderByDescending(n => n).Skip(3); //先倒排序, 再取第 3 个元素之后的    var R4 = nArr.OrderBy(n => n).SkipWhile(n => n <= 3);   //先排序(123345), 从不满足条件开始, 之后的    var R5 = nArr.SkipWhile((num, index) => num != index); // 从第二个元素开始, 数字和序号就不一样了    string s1 = string.Join("", R1); //435    string s2 = string.Join("", R2); //345    string s3 = string.Join("", R3); //321    string s4 = string.Join("", R4); //45    string s5 = string.Join("", R5); //2435    TextBox1.Text = string.Format("{0}\n{1}\n{2}\n{3}\n{4}", s1, s2, s3, s4, s5);}//Take、TakeWhile 用法同上, 只是获取之前的protected void Button2_Click(object sender, EventArgs e){    int[] nArr = { 1, 3, 2, 4, 3, 5 };    var R1 = nArr.Take(3);    var R2 = nArr.OrderBy(n => n).Take(3);    var R3 = nArr.OrderByDescending(n => n).Take(3);    var R4 = nArr.OrderBy(n => n).TakeWhile(n => n <= 3);    var R5 = nArr.TakeWhile((num, index) => num != index);    string s1 = string.Join("", R1); //132    string s2 = string.Join("", R2); //123    string s3 = string.Join("", R3); //543    string s4 = string.Join("", R4); //1233    string s5 = string.Join("", R5); //13    TextBox1.Text = string.Format("{0}\n{1}\n{2}\n{3}\n{4}", s1, s2, s3, s4, s5);}

All 与 Any:

//都满足条件时 All 才返回 Trueprotected void Button1_Click(object sender, EventArgs e){    int[] nArr = { 1, 3, 5, 7, 9 };    bool b1 = nArr.All(n => n % 2 == 0); //False    bool b2 = nArr.All(n => n % 2 == 1); //True    TextBox1.Text = string.Concat(b1, "\n", b2);}//其中一个满足条件 Any 就返回 Trueprotected void Button2_Click(object sender, EventArgs e){    string str1 = "Delphi";    string str2 = "Asp.Net";    string str3 = "";    bool b1 = str1.Any();              //True    bool b2 = str2.Any();              //True    bool b3 = str3.Any();              //False    bool b4 = str1.Any(c => c == 'D'); //True    bool b5 = str2.Any(c => c == 'D'); //False    bool b6 = str2.Any(c => c == 'D'); //False    TextBox1.Text = string.Concat(b1, "\n", b2, "\n", b3, "\n", b4, "\n", b5, "\n", b6);}

是否包含(Contains):

protected void Button1_Click(object sender, EventArgs e){    string str = "Asp.Net 4.0";    bool b1 = str.Contains('4');       //True    bool b2 = str.Contains("Net 4.0"); //True    bool b3 = str.Contains("Net4.0");  //False    TextBox1.Text = string.Concat(b1, "\n", b2, "\n", b3, "\n");}

获取只是唯一的元素(Single、SingleOrDefault):

protected void Button1_Click(object sender, EventArgs e){    string str = "Microsoft";    char c1, c2, c3, c4, c5, c6;    c1 = c2 = c3 = c4 = c5 = c6 = '*';    //Single    c1 = str.Single(c => c == 'M'); //M    try { c2 = str.Single(c => c == 'o'); }    catch (Exception err) { Response.Write(err.Message + "<br/>"); } // 序列包含一个以上的匹配元素     try { c3 = str.Single(c => c == 'A'); }    catch (Exception err) { Response.Write(err.Message + "<br/>"); } // 序列不包含任何匹配元素    //SingleOrDefault    c4 = str.SingleOrDefault(c => c == 'M'); //M    try { c5 = str.SingleOrDefault(c => c == 'o'); }    catch (Exception err) { Response.Write(err.Message + "<br/>"); } // 序列包含一个以上的匹配元素     c6 = str.SingleOrDefault(c => c == 'A'); // 这不会激发异常    TextBox1.Text = string.Format("{0}{1}{2}{3}{4}{5}", c1, c2, c3, c4, c5, c6); //M**M*}

指定默认空值(DefaultIfEmpty):

protected void Button1_Click(object sender, EventArgs e){    string str1 = "Asp.Net 3.5";    string str2 = "";    string r1 = string.Join("|", str1.DefaultIfEmpty());    //A|s|p|.|N|e|t| |3|.|5    string r2 = string.Join("|", str2.DefaultIfEmpty());    //    string r3 = string.Join("|", str2.DefaultIfEmpty('*')); //*    TextBox1.Text = string.Concat(r1, "\n", r2, "\n", r3);}

学用 ASP.Net 之 "字符串" (4): string 类的扩展方法

学用 ASP.Net 之 "字符串" (4): string 类的扩展方法

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