C# - 反射对象

反射对象用于在运行时获取类型信息，允许访问正在运行的程序的元数据的类位于System.Reflection命名空间中。

System.Reflection命名空间包含允许您获取有关应用程序的信息并动态向应用程序添加类型、值和对象的类。

查看元数据

需要初始化System.Reflection类的MemberInfo对象以发现与类关联的属性。为此，将目标类的对象定义为-

System.Reflection.MemberInfo info = typeof(MyClass);

以下程序演示了此-

using System;

[AttributeUsage(AttributeTargets.All)]
public class HelpAttribute : System.Attribute {
   public readonly string Url;
   
   public string Topic   //Topic is a named parameter {
      get {
         return topic;
      }
      set {
         topic = value;
      }
   }
   public HelpAttribute(string url)   //url is a positional parameter {
      this.Url = url;
   }
   private string topic;
}

[HelpAttribute("Information on the class MyClass")]
class MyClass {

}

namespace AttributeAppl {
   class Program {
      static void Main(string[] args) {
         System.Reflection.MemberInfo info = typeof(MyClass);
         object[] attributes = info.GetCustomAttributes(true);
         
         for (int i = 0; i < attributes.Length; i++) {
            System.Console.WriteLine(attributes[i]);
         }
         Console.ReadKey();
      }
   }
}

编译并运行时，它显示附加到类MyClass-的自定义属性的名称

HelpAttribute

在本例中，无涯教程使用上一章中创建的DeBugInfo属性，并使用反射读取Rectangle类中的元数据。

链接：https://www.learnfk.comhttps://www.learnfk.com/csharp/csharp-reflection.html

来源：LearnFk无涯教程网

using System;
using System.Reflection;

namespace BugFixApplication {
   //要分配给类及其成员的自定义属性 BugFix
   [AttributeUsage(
      AttributeTargets.Class |
      AttributeTargets.Constructor |
      AttributeTargets.Field |
      AttributeTargets.Method |
      AttributeTargets.Property,
      AllowMultiple = true)]

   public class DeBugInfo : System.Attribute {
      private int bugNo;
      private string developer;
      private string lastReview;
      public string message;
      
      public DeBugInfo(int bg, string dev, string d) {
         this.bugNo = bg;
         this.developer = dev;
         this.lastReview = d;
      }
      public int BugNo {
         get {
            return bugNo;
         }
      }
      public string Developer {
         get {
            return developer;
         }
      }
      public string LastReview {
         get {
            return lastReview;
         }
      }
      public string Message {
         get {
            return message;
         }
         set {
            message = value;
         }
      }
   }
   [DeBugInfo(45, "Zara Ali", "12/8/2012", Message = "Return type mismatch")]
   [DeBugInfo(49, "Nuha Ali", "10/10/2012", Message = "Unused variable")]
   
   class Rectangle {
      //member variables
      protected double length;
      protected double width;
      
      public Rectangle(double l, double w) {
         length = l;
         width = w;
      }
      [DeBugInfo(55, "Zara Ali", "19/10/2012", Message = "Return type mismatch")]
      public double GetArea() {
         return length * width;
      }
      [DeBugInfo(56, "Zara Ali", "19/10/2012")]
      public void Display() {
         Console.WriteLine("Length: {0}", length);
         Console.WriteLine("Width: {0}", width);
         Console.WriteLine("Area: {0}", GetArea());
      }
   }//end class Rectangle
   
   class ExecuteRectangle {
      static void Main(string[] args) {
         Rectangle r = new Rectangle(4.5, 7.5);
         r.Display();
         Type type = typeof(Rectangle);
         
         //iterating through the attribtues of the Rectangle class
         foreach (Object attributes in type.GetCustomAttributes(false)) {
            DeBugInfo dbi = (DeBugInfo)attributes;
            
            if (null != dbi) {
               Console.WriteLine("Bug no: {0}", dbi.BugNo);
               Console.WriteLine("Developer: {0}", dbi.Developer);
               Console.WriteLine("Last Reviewed: {0}", dbi.LastReview);
               Console.WriteLine("Remarks: {0}", dbi.Message);
            }
         }
         
         //iterating through the method attribtues
         foreach (MethodInfo m in type.GetMethods()) {
            
            foreach (Attribute a in m.GetCustomAttributes(true)) {
               DeBugInfo dbi = (DeBugInfo)a;
               
               if (null != dbi) {
                  Console.WriteLine("Bug no: {0}, for Method: {1}", dbi.BugNo, m.Name);
                  Console.WriteLine("Developer: {0}", dbi.Developer);
                  Console.WriteLine("Last Reviewed: {0}", dbi.LastReview);
                  Console.WriteLine("Remarks: {0}", dbi.Message);
               }
            }
         }
         Console.ReadLine();
      }
   }
}

编译并执行上述代码时，将生成以下输出-

无涯教程网

Length: 4.5
Width: 7.5
Area: 33.75
Bug No: 49
Developer: Nuha Ali
Last Reviewed: 10/10/2012
Remarks: Unused variable
Bug No: 45
Developer: Zara Ali
Last Reviewed: 12/8/2012
Remarks: Return type mismatch
Bug No: 55, for Method: GetArea
Developer: Zara Ali
Last Reviewed: 19/10/2012
Remarks: Return type mismatch
Bug No: 56, for Method: Display
Developer: Zara Ali
Last Reviewed: 19/10/2012
Remarks: