C# 6.0新特性
作者：互联网
C# 6.0新特性
01.自动属性新初始化方法
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6 namespace NewDemo
7 {
8 //以前用法：自动属性不能在声明的时候初始化
9 //class Student
10 //{
11 // public Student()
12 // {
13 // StudentId = 1001;
14 // Name = "张欣欣";
15 // Age = 25;
16 // }
17 // public int StudentId { get; set; }
18 // public string Name { get; set; }
19 // public int Age { get; set; }
20 // public string Gender
21 // {
22 // get { return Gender; }
23 // }
24 //}
25 //新用法：声明的同时可以初始化，并且允许只读属性初始化
26 class Student
27 {
28 public int StudentId { get; set; } = 1001;
29 public string Name { get; set; } = "张欣欣";
30 public int Age { get; set; } = 25;
31 public string Gender { get; } = "男";
32 }
33 }
View Code
02.String.Format的简化
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6 namespace NewDemo
7 {
8 class NewFormat
9 {
10 //旧用法：string.Format("{0},{1}",变量1，变量2)实现格式化输出
11 public void OldMethod()
12 {
13 Student objStudent = new NewDemo.Student();
14 string s1 = string.Format("{0},{1}", objStudent.Name, objStudent.Age);
15 string s2 = string.Format("姓名={0},年龄={1}", objStudent.Name, objStudent.Age);
16 Console.WriteLine("{0},\r\n{1}", s1, s2);
17 Console.WriteLine();
18 string s3 = string.Format("{0,10},{1:d3}", objStudent.Name, objStudent.Age);
19 string s4 = string.Format("{0,10},{1,10:d3}", objStudent.Name, objStudent.Age);
20 Console.WriteLine("{0},\r\n{1}", s3, s4);
21 Console.WriteLine();
22 string s5 = string.Format("{0:yyyy-MM-dd}", DateTime.Now);
23 Console.WriteLine(s5);
24 Console.WriteLine();
25 string sql = "select Name from Students where StudentId={0} and Age>{1}";
26 Console.WriteLine(sql, objStudent.StudentId, objStudent.Age);
27 }
28 //新用法：在字符串前面添加“$”前缀，（变量可以直接写到{}内，并且有很强的智能提示）
29 public void NewMethod()
30 {
31 Student objStudent = new NewDemo.Student();
32 string s1 = $"{objStudent.Name },{objStudent.Age }";
33 string s2 = $"姓名={objStudent.Name },年龄={objStudent.Age }";
34 Console.WriteLine($"{ s1} ,\r\n{ s2} ");
35 string s3 = $"{objStudent.Name,10},{objStudent.Age:d3}";
36 string s4 = $"{objStudent.Name,10},{objStudent.Age,10:d3}";
37 Console.WriteLine($"{ s3} ,\r\n{ s4} ");
38 string s5 = $"{DateTime.Now:yyyy-MM-dd}";
39 Console.WriteLine(s5);
40 //典型应用
41 string sql = $"select Name from Students where StudentId={objStudent.StudentId} and Age>{objStudent.Age }";
42 Console.WriteLine( sql);
43 }
44 }
45 }
View Code
03.表达式属性和表达式方法
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6 namespace NewDemo
7 {
8 /// <summary>
9 /// 表达式应用的新特性
10 /// </summary>
11 class ExpressionApp
12 {
13 //【1】表达式属性：只有一个get访问器的单行属性可以使用lambda语法编写
14 public DateTime Birthday { get; set; } = Convert.ToDateTime("1990-1-10");
15 //public int Age
16 //{
17 // get { return DateTime.Now.Year - Birthday.Year; }
18 //}
19 public int Age => DateTime.Now.Year - Birthday.Year;
20 //【2】表达式方法：只有一条语句的方法可以使用lambda语法编写
21 //public int Add(int a, int b)
22 //{
23 // return a + b;
24 //}
25 public int Add(int a, int b) => a + b;
26 }
27 }
View Code
04.泛型集合Dictionary初始化
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6 namespace NewDemo
7 {
8 /// <summary>
9 /// 泛型集合的新初始化方法
10 /// </summary>
11 class NewCollectionInit
12 {
13 public Dictionary<string, int> OldMethod()
14 {
15 Dictionary<string, int> student = new Dictionary<string, int>();
16 student.Add("张三", 25);
17 student.Add("李四", 34);
18 student.Add("王五", 26);
19 return student;
20 }
21 //新的初始化方法
22 public Dictionary<string, int> NewMethod()
23 {
24 Dictionary<string, int> student = new Dictionary<string, int>()
25 {
26 ["张三"] = 25,
27 ["李四"] = 34,
28 ["王五"] = 26
29 };
30 return student;
31 }
32 }
33 }
View Code
05.static声明静态类的引用
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6 using static System.Math;
7
8 namespace NewDemo
9 {
10 /// <summary>
11 /// static声明静态类的引用
12 /// </summary>
13 class StaticClassApp
14 {
15 //以前用法：两个数的绝对值相加
16 public static int OldMethod(int a, int b)
17 {
18 return Math.Abs(a) + Math.Abs(b);
19 }
20 //现在用法：使用using static System.Math;提前引入静态类，避免每次都调用Math类
21 public static int NewMethod1(int a, int b)
22 {
23 return Abs(a) + Abs(b);
24 }
25 public static int NewMethod2(int a, int b) => Abs(a) + Abs(b);
26 }
27 }
View Code
06.nameof表达式
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6 namespace NewDemo
7 {
8 /// <summary>
9 /// nameof表达式
10 /// </summary>
11 class NameofExpressions
12 {
13 //以前用法：当参数名称变化的时候，被引用地方需要同步修改
14 public void OldMethod(int account)
15 {
16 if (account < 100)
17 {
18 throw new ArgumentException("参数account的值不能小于100！");
19 }
20 else
21 {
22 //其他操作...
23 }
24 }
25 //新用法：使用nameof，当参数变化时会在引用的地方同步变化，避免程序的硬编码
26 //nameof里面可以是：类名、方法名、参数名、属性名
27 public void NewMethod(int account)
28 {
29 if (account < 100)
30 {
31 throw new ArgumentException($"参数{nameof(account)}的值不能小于100！");
32 }
33 else
34 {
35 //其他操作...
36 }
37 }
38 }
39 }
View Code
07.Null条件表达式
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6 namespace NewDemo
7 {
8 /// <summary>
9 /// null操作符：null传递操作符简化了空值的检查
10 /// </summary>
11 class NullOperator
12 {
13 string[] sArray = new string[] { "bc", "cde", null, "efgg", null };
14 //以前用法
15 public void OldMethod()
16 {
17 foreach (string item in sArray)
18 {
19 var length = item == null ? 0 : item.Length;
20 Console.WriteLine(length);
21 }
22 Console.WriteLine("---");
23 }
24 //新方法：
25 public void NewMethod()
26 {
27 foreach (string item in sArray)
28 {
29 var length = item?.Length;//如果为null直接输出null
30 Console.WriteLine(length);
31 }
32 Console.WriteLine("---");
33 foreach (string item in sArray)
34 {
35 var length = item?.Length ?? 0;
36 Console.WriteLine(length);
37 }
38 }
39 }
40 }
View Code
END
标签：string,C#,System,特性,int,6.0,using,objStudent,public 来源： https://www.cnblogs.com/zeon/p/16324839.html