C# 反射Reflection应用与实践指南

using System;
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public class HelpAttribute : Attribute
{
    public string Url { get; }
    public string Topic { get; set; }
    public HelpAttribute(string url)
    {
        Url = url;
    }
}
[HelpAttribute("https://www.example.com", Topic = "Class Documentation")]
class MyClass
{
}
class Program
{
    static void Main()
    {
        Type type = typeof(MyClass);
        var attributes = type.GetCustomAttributes(false);
        foreach (var attribute in attributes)
        {
            if (attribute is HelpAttribute helpAttr)
            {
                Console.WriteLine($"Help URL: {helpAttr.Url}");
                Console.WriteLine($"Topic: {helpAttr.Topic}");
            }
        }
    }
}

using System;
using System.Reflection;
[AttributeUsage(AttributeTargets.Class | 
                AttributeTargets.Method |
                AttributeTargets.Property |
                AttributeTargets.Field, AllowMultiple = true)]
public class DeBugInfo : Attribute
{
    public int BugNo { get; }
    public string Developer { get; }
    public string LastReview { get; }
    public string Message { get; set; }
    public DeBugInfo(int bugNo, string developer, string lastReview)
    {
        BugNo = bugNo;
        Developer = developer;
        LastReview = lastReview;
    }
}
[DeBugInfo(101, "John Doe", "2021-10-10", Message = "Initial version")]
class MyClass
{
    [DeBugInfo(102, "Jane Doe", "2021-11-11", Message = "Refactored code")]
    public void MyMethod() { }
}
class Program
{
    static void Main()
    {
        Type type = typeof(MyClass);
        // 获取类上的特性
        foreach (var attr in type.GetCustomAttributes(false))
        {
            if (attr is DeBugInfo dbi)
            {
                Console.WriteLine($"Bug No: {dbi.BugNo}, Developer: {dbi.Developer}, Last Review: {dbi.LastReview}, Message: {dbi.Message}");
            }
        }
        // 获取方法上的特性
        foreach (var method in type.GetMethods())
        {
            foreach (var attr in method.GetCustomAttributes(false))
            {
                if (attr is DeBugInfo dbi)
                {
                    Console.WriteLine($"Bug No: {dbi.BugNo}, Method: {method.Name}, Developer: {dbi.Developer}, Last Review: {dbi.LastReview}, Message: {dbi.Message}");
                }
            }
        }
    }
}