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);
}
ASP.Net string 类的扩展方法 [转]
时间： 2024-10-09 04:18:41