C#2.0
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泛型
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部分类型
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匿名方法
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迭代器
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可空类型
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Getter / setter单独可访问性
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方法组转换(代表)
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Co- and Contra-variance for delegates
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静态类
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Delegate inference
C#3.0
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隐式类型局部变量
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对象和收集初始化器
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自动实现的属性
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匿名类型
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扩展方法
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查询表达式
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Lambda表达式
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表达树
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部分方法
C#4.0
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动态绑定
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命名和可选参数
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Generic co- and contravariance
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嵌入式互操作类型(“NoPIA”)
C#5.0
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异步方法
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Caller info attributes
C#6.0
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Compiler-as-a-service(Roslyn)
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将静态类型成员导入命名空间
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异常过滤器
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在Catch和Finally中使用Await
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自动属性初始化器
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只读属性的默认值
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Expression-bodied members
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Null-conditional operators(空条件运算符,简洁检查)
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字符串插值
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nameof operator
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字典初始化器
C#7.0
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out变量
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模式匹配
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元组
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解构
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局部函数
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数字分隔符
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二进制文字
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局部引用和引用返回
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扩展异步返回类型
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表达式的构造函数和finalizers
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Expression bodied getters and setters
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throw表达式
c#7.0新特性详解
C#7.0增加许多新功能,重点是数据,代码简化和性能上。
Out variables
目前在C#中,使用out参数不像我们想要的那么流畅。在使用out参数调用一个方法之前,首先必须声明变量来传递给它。您也不能使用var
它们来声明它们,但需要指定完整的类型。
public void PrintCoordinates(Point p) { int x, y; //必须声明 p.GetCoordinates(out x, out y); WriteLine($"({x}, {y})"); }
在c#7中
public void PrintCoordinates(Point p) { p.GetCoordinates(out int x, out int y); WriteLine($"({x}, {y})"); }
模式匹配
以前版本需要转化
public static void PrintStars(object o) { if (o is int) Console.WriteLine(Convert.ToInt32(o) + 12); }
在c#7中
public static void PrintStars(object o) { if (o is int i)
Console.WriteLine(i + 12); }
Switch statements with patterns 扩展switch语句使用模式匹配
public static void PrintStars(object o)
{
switch (o)
{
case Print p:
break;
case int a:
break;
case String b when b=="123":
break;
}
}
}
元组(Tuples)
元组依赖于一组基础类型,不包括在预览4中。要使功能正常工作,您可以通过NuGet轻松获取它们:
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右键单击解决方案资源管理器中的项目,然后选择“管理NuGet软件包...”
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选择“浏览”选项卡,选中“包含预发行”,然后选择“nuget.org”作为“包源”
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搜索“System.ValueTuple”并安装它。
static void Main(string[] args)
{
var tuple = (a: 10, b: "123");
Console.WriteLine($"a:{tuple.a},b:{tuple.b}");
var result1 = GetS();
var result = Get();
Console.WriteLine($"Item1:{result1.Item1},Item2:{result1.Item2},Item3:{result1.Item3}");
Console.WriteLine($"a:{result.a},b:{result.b},c:{result.c}");
Console.ReadLine();
}
static (string, int, DateTime) GetS()
{
return ("abc", 123, DateTime.Now);
}
static (string a, int b, DateTime c) Get()
{
return (a: "abc", b: 123, c: DateTime.Now);
}
部函数
简单的说,就是在方法里面写方法然后自己调用。
static void Main(string[] args) { Console.WriteLine($"{Get(123)},{Get("abc")},{Get(null)}"); Console.ReadLine(); } public static string Get(object a) { return GetP(); string GetP() { if (a is int v) return v + ""; if (a is string b) return b; return "ccc"; } }
Literal improvements
C#7.0允许在数字文字中_
作为数字分隔符出现:
var d = 123_456; var x = 0xAB_CD_EF;
你可以把它们放在数字之间,以提高可读性。它们对价值没有影响。另外,C#7.0引入了二进制文字,因此您可以直接指定位模式,而不必以心脏知道十六进制符号。
var b = 0b1010_1011_1100_1101_1110_1111;
更多c#7.0的特性
请参考文档:https://blogs.msdn.microsoft.com/dotnet/2016/08/24/whats-new-in-csharp-7-0/
c#6.0新语言功能详解
以下新功能在VS 2015及17中实现并可用
字符串格式化
上面的代码中都有体现。
public void Main()
{
int i = 1;
string s = "id";
Console.WriteLine($"{s}-{i}");
}
字典索引初始化
var numbers = new Dictionary<int, string> { [7] = "seven", [9] = "nine", [13] = "thirteen" };
自动属性初始化
public class Customer { public string First { get; set; } = "Jane"; public string Last { get; set; } = "Doe"; }
using引用静态类
If you have a static class, whose members you are using a lot you can now avoid typing the class name everytime by including the class in the using declaration.
using static System.Console; using static System.Math; using static System.DayOfWeek; class Program { static void Main() { WriteLine(Sqrt(3*3 + 4*4)); WriteLine(Friday - Monday); } }
Exception Filters
Exception filters allow you to add additional conditions to exception handlers. We can now write an if a when statement next to a catch block & the catch block will only get executed if the condition returns true. Below is an impractical & silly example to play around with.
public void Main()
{
try
{
throw new Exception("E2");
}
catch(Exception ex) when (ex.Message == "E1")
{
Console.WriteLine("caught E1");
}
catch(Exception ex) when (ex.Message == "E2")
{
Console.WriteLine("caught E2");
}
}
Using await in catch and finally blocks
We can now await functions in catch and finally blocks. This was not allowed prior to C# 6.0
public void Main()
{
BuggyFunctionAsync();
Console.WriteLine("done!");
Thread.Sleep(2000);
}public async void BuggyFunctionAsync()
{
try { throw new Exception(); }
catch
{
Console.WriteLine("entering catch block");
await Task.Delay(1000);
Console.WriteLine("exiting catch block");
}
finally
{
Console.WriteLine("entering finally block");
await Task.Delay(1000);
Console.WriteLine("exiting finally block");
}
}
The nameof Operator
There are times when we need the name of a variable in string form. nameof operator does just that. It takes a variable and converts the variable name to string.
public void Main()
{
Console.WriteLine(nameof(Account));
Console.WriteLine(nameof(Account.AccountNumber));
}class Account
{
public int AccountNumber{get; set;}
}
Null Conditional Operator
if(node==null || node.Children == null)
Console.WriteLine("Invalid Node");
if(node?.Children == null)
Console.WriteLine("Invalid Code");
c#2.0-5.0参考文档
c#5.0参考文档
c#4.0参考文档
连接地址:https://msdn.microsoft.com/en-us/magazine/ff796223.aspx
c#3.0参考文档
连接地址:https://msdn.microsoft.com/en-us/library/bb308966.aspx
c#2.0参考文档
连接地址:https://msdn.microsoft.com/en-us/library/7cz8t42e(v=vs.80).aspx