[C#] 语法之Attribute

在c#中,定义类的成员,可以定义Property称为属性.Attribute就称为特性.

在FCL中,有内置的Attribute.如:

Condition[Attribute]:在什么条件可以调用.(只能作用于返回值为void的方法上)

Obsolete:方法弃用.支持禁用.

代码1:

class Program
    {
        static void Main(string[] args)
        {
            Func();
            Console.ReadLine();
        }

        [Obsolete("you can use Func to replace this",true)]
        private static void Test()
        {
            Console.WriteLine("noooo");
        }

        private static void Func()
        {
            Console.WriteLine("yesss");
        }
    }
    class T
    {
        [Conditional("DEBUG")]
        public static void M(string str)
        {
            Console.WriteLine("Method{0}", str);
        }
    }

自定义Attribute:

代码2:

[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
    public class HelpAttribute : Attribute
    {
        public HelpAttribute(string str)
        {
            HelpStr = str;
        }
        public string Name { get; set; }
        public string HelpStr { get; set; }
    }

AttributeTargets.Class：作用目标只能是类.

AllowMultiple:是否可以在一个元素上多次作用特性.

Inherited:当目标被继承时,特性是否也继承.

反射获取类的Attribute信息:

代码3:

class Program
    {
        static void Main(string[] args)
        {
            var attrs = typeof(MyClass).GetCustomAttributes(false);
            for (int i = 0; i < attrs.Length; i++)
            {
                var attr = attrs[i] as HelpAttribute;
                if (attr != null) Console.WriteLine(attr.HelpStr + attr.Name);
            }
            Console.ReadLine();
        }
    }

    [Help("good", Name = " class")]
    class MyClass
    {

    }