首页 > 其他分享 >string 类的扩展方法

string 类的扩展方法

时间:2022-11-27 11:05:22浏览次数:38  
标签:Join string 扩展 nArr Person str var 方法


 

​​string 类的扩展方法​​


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 Int64
Max<> //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 null
FirstOrDefault <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):



//Concat
protected 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);
}

//Zip
protected 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);
}

//Join
protected 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):



//Select
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.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 SelectMany
protected 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:
11
AA
DD
GG
22
BB
EE
33
CC
FF
----------
11
AA:11
DD:11
GG:11
22
BB:22
EE:22
33
CC:33
FF: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、SkipWhile
protected 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 True
protected 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 True
protected 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);
}


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 Int64
Max<> //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 null
FirstOrDefault <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):



//Concat
protected 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);
}

//Zip
protected 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);
}

//Join
protected 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):



//Select
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.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 SelectMany
protected 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:
11
AA
DD
GG
22
BB
EE
33
CC
FF
----------
11
AA:11
DD:11
GG:11
22
BB:22
EE:22
33
CC:33
FF: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、SkipWhile
protected 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 True
protected 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 True
protected 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);
}

标签:Join,string,扩展,nArr,Person,str,var,方法
From: https://blog.51cto.com/u_15834343/5889829

相关文章

  • abap-BAPI_MATERIAL_SAVEDATA 扩展字段的使用
    事情原由:需要用jco来调用 BAPI_MATERIAL_SAVEDATA创建物料,但是发现有个可配置栏位,没有地方传入这个bapi.imports和tables里都没办法将这个字段传入,检查了一下......
  • Java中Collections.sort()方法详解
     时间:2022/11/27 在我们写算法题的时候有时需要对给定的List列表进行排序,这样方便之后的操作,此时我们可以用到Collections类中的sort方法,JavaAPI文档中对该方......
  • JavaScript中String的match方法详解
     String.prototype.match()**String.prototype.match()方法返回通过一个正则表达式匹配到的字符串结果。**​​var='Thequickbrownfoxjumpsoverthelazydog.Itba......
  • 【Amadeus原创】Win10底部任务栏卡死的终极解决方法
    原因:微软自带的资讯和兴趣因国内网络限制,造成失效。解决方案:底部右键-》资讯和兴趣-》关闭。以上仅限WIn10操作系统,win11操作系统以上忽略。......
  • Chrome 浏览器安装Vue插件方法
    谷歌浏览器扩展程序首先去github下载vue.zip文件插件 下载地址:https://github.com/vuejs/vue-devtools不要去下载默认分支的下载后解压验证npm是否安装成功命令,......
  • 完整解决方案:让你的IIS 支持PHP方法
    目前很多​​站长​​都开始使用PHP来编写网站代码,而且目前开源的PHP系统也很多,但是MSIIS(internetinformationsystem)并不支持PHP,这给我们调试和使用PHP站点带来了很多困......
  • 构造方法的标准使用方法
      /*有参构造的使用方法:new后面的类名()括号内就是构造方法中你要传进去的实际参数构造器方法中的括号内的参数那都是形式参数*//*总结:使用构造器输出的基本操作......
  • 集合的常用的方法
    /*需求:学会使用集合的常用方法1.A.remove()删除指定集合中的值,并且返回ture或者false,括号里写你想要删除的值2.A.remove()删除指定索引处集合中的值,并且返回被删除的集......
  • StringBuilder_append方法
      /*总结:StringBuilder类中的reverse方法:反转字符串的方法StringBuilder类中的append()方法:在括号内添加数据,并且返回给对象本身*/......
  • 运用StringBuilder类中的reverse来反转数组
      /*其实不转换为String也行,运用StringBuilder输出即可比自己定义的String来反转更加简单方便也可以一次性输出定义出来这个反转方法通过匿......