c#10 语法特性

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theme: smartblue

一、 属性拓展

创建实体类

``` public class Student { public int Id { get; set; } = 24;

public string Name { get; set; } = "xyy";public Address address { get; set; }
}public class Address
{public string position { get; set; }
}

``` 当一个类为 object 且要根据某个属性进行筛选时

``` object obj = new Student { address = new Address { position = "anhui" } };

if(obj is Student { address :{position:"anhui" } }) { Console.WriteLine("anhui"); }

```

二、 lambda 表达式改进

2.1 调用特性内的方法

自定义特性 public class TestAttribute:Attribute { public void Show() { Console.WriteLine($"{this.GetType().FullName} was build."); } } 调用特性内的方法

var f1 = [TestAttribute] () =>{}; MethodInfo methodInfo = f1.GetMethodInfo(); TestAttribute testAttribute = methodInfo.GetCustomAttribute<TestAttribute>(); testAttribute.Show();

2.2 调用静态修饰的特性内方法

var f1 = [TestAttribute] static (int x) =>x; MethodInfo methodInfo = f1.GetMethodInfo(); TestAttribute testAttribute = methodInfo.GetCustomAttribute<TestAttribute>(); testAttribute.Show();

2.3 调用有返回值的特性内方法

var f1 = [DoesNotReturn:TestAttribute] (int x) =>x; ICustomAttributeProvider returnTypeCustomAttributes = f1.GetMethodInfo().ReturnTypeCustomAttributes; object[] objects = returnTypeCustomAttributes.GetCustomAttributes(typeof(TestAttribute),true); foreach(TestAttribute attrbute in objects) { attrbute.Show(); }

三、 常数内插字符串

``` const string firstName = "f"; const string lastName = "l"; const string name = $"{firstName} {lastName}";

```