C# 语法糖测试--未完待续

/// <summary>
/// string扩展方法，可以用字符串变量加.的形式直接调用，this是关键
/// </summary>
public static class StringExtention
{
    private static Regex regex = new Regex("\\d+");
    public static bool IsNumber(this string s)
    {
        if (string.IsNullOrEmpty(s)) return false;
        return regex.IsMatch(s);
    }
    public static bool IsNullOrEmpty(this string s)
    {
        if (s == null|| s == "") return true;
        return false;
    }
}

void Test()
    {
        //?可空值类型，??空合并运算符
        int? a = null;//a是可空的int类型
        int? b = 100;
        int? c = a ?? b;//a为null，返回b
        Debug.Log(c);//输出100
        string s1 = null;
        string s2 = "ByeBye";
        string s3 = s1 ?? s2;//s1为null，返回s2
 
        //?判空运算符
        Debug.Log(s1.Length);//报错
        Debug.Log(s1?.Length);//输出null
        Debug.Log($"s1?.Length:{s1?.Length}");//未输出{}内的值
 
        //集合判空运算符？[]
        List<string> petList = new List<string> { "Dog", "Cat", "Bear", "Snake" };
        Debug.Log(petList?[0]);//输出Dog
        petList = null;
        Debug.Log(petList?[0]);//输出Null，不报错；用于判断数组集合是否为空
 
        //扩展方法
        string s = "123";
        Debug.Log(s.IsNumber());//输出True
        Debug.Log(s.IsNullOrEmpty());//输出False
 
        //遍历List
        List<int> list = new List<int> { 1, 2, 3, 4 };
        list.ForEach(item => Debug.Log(item));
 
        //匿名类
        var user = new { Name = "Tome", Age = 18, Sex = "Male" };
        //匿名方法
        Action<string> p = delegate (string s) { Debug.Log(s); };
        p("你好啊");
 
    }