c#语法糖253

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  1. abstract类最好用来声明公共const变量
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class Bad
{
    abstract class MathConstants
    {
        public static readonly double Pi = 3.14;
    }
 
    class Circle : MathConstants
    {
        private double radius;
 
        public double Area() => Math.Pow(radius, 2) * Pi;
    }
}
  1. ReadOnlyCollection替换Array的readonly
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//错误
class Bad
{
    public static readonly string[] Foo = { "hello", "world" };
    public static void Main(string[] args)
    {
        Foo[0] = "goodbye";
    }
}
//对的
class Good
{
    public static readonly ReadOnlyCollection<string> Foo
        = new ReadOnlyCollection<string>(new string[] { "hello", "world" });
    public static void Main(string[] args)
    {
 
    }
}
  1. Assembly的代码
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public class AssemblyPathInjectionHandler : IHttpHandler {
  public void ProcessRequest(HttpContext ctx) {
    string configType = ctx.Request.QueryString["configType"];
 
    if (configType.equals("configType1") || configType.equals("configType2")) {
      // GOOD: Loaded assembly is one of the two known safe options
      var safeAssembly = Assembly.LoadFile(@"C:\SafeLibraries\" + configType + ".dll");
 
      // Code execution is limited to one of two known and vetted assemblies
      MethodInfo m = safeAssembly.GetType("Config").GetMethod("GetCustomPath");
      Object customPath = m.Invoke(null, null);
      // ...
    }
  }
}

  1. Cyclomatic Complexity(圈复杂度)

  2. dynamic 弱语言的东西类似js的结构体，和模板搭配很好用

  3. Obsolete

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    [Obsolete("该方法已被弃用，请使用NewMethod代替")]
    static void OldMethod()

  4. abstract属性可以通过继承覆盖
    ···
    public abstract class Shape
    {
    private string name;

    public Shape(string s)
    {

    // calling the set accessor of the Id property.
Id = s;

    }
    public string Id
    {

    get
{
    return name;
}

set
{
    name = value;
}

    }

    // Area is a read-only property - only a get accessor is needed:
    public abstract double Area
    {

    get;

    }

    public override string ToString()
    {

    return $"{Id} Area = {Area:F2}";

    }
    }
    public class Square : Shape
    {
    private int side;

    public Square(int side, string id)

    : base(id)

    {

    this.side = side;

    }

    public override double Area
    {

    get
{
    // Given the side, return the area of a square:
    return side * side;
}

    }
    }

···

  1. is的规则

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    interface Animal { }
    class Cat : Animal { }
    class Dog : Animal { }
    static void Main(string[] args)
    {
        List<Animal> animals = new List<Animal> { new Cat(), new Dog() };
        foreach (Animal a in animals)
        {
            if (a is Cat)
                Console.WriteLine("Miaow!");
            if (a is Dog)
                Console.WriteLine("Woof!");
            if (a is Animal)
                Console.WriteLine("Animal!");
        }
        Console.ReadLine();
        Console.ReadKey();
    }// Miaow Animal Woof Animal

  2. 引用用类型,值类型比较

引用类型:
ReferenceEquals(null, x)比较是否是指向同一内存
虚函数Equals

值类型:
==运算符比较

  1. 双重检查lock
// //