Question

My intention is to have a class T, that has several static readonly instances of its own type. What I am now trying to do is to create a generic method that will recognize all those instances and add them to a list. So far I could locate all the elements, and the FieldInfo.FieldHandle.Value seems to contain the object, but I am yet unskilled in getting it. Maybe it is wrong to use FieldInfo. Can anyone give me a hand?

(Thanks!) Here is the code example (with solution applied):

using System;
using System.Collections.Generic;
using System.Reflection;

namespace PickStatic {
  class Fruit {
    public static readonly Fruit Orange = new Fruit("Orange");
    public static readonly Fruit Kiwi = new Fruit("Kiwi");
    public static readonly Fruit Pear = new Fruit("Pear");

    public string name { set; get; }

    public Fruit(string name) {
      this.name = name;
    }

    public static List<T> getAll<T>() where T : class {
      List<T> result = new List<T>();
      MemberInfo[] members = typeof(T).GetMembers();
      foreach(MemberInfo member in members) {
        if(member is FieldInfo) {
          FieldInfo field = (FieldInfo) member;
          if(field.FieldType == typeof(T)) {
            T t = (T) field.GetValue(null);
            result.Add(t);
          }
        }
      }
      return result;
    }

    public static void Main(string[] args) {
      List<Fruit> fruits = getAll<Fruit>();
      foreach(Fruit fruit in fruits) {
        Console.WriteLine("Loaded: {0}", fruit.name);
      }
      Console.ReadLine();
    }
  }
}

The class Fruit contains three static objects of type Fruit. It is being attempted to get the list of all such objects using a generic method.

Answer 1

You need to use the FieldInfo.GetValue method.

Invoke it with null (Since it’s a static field)

Edit : It is not recommended to use reflection in “Critical” sections of the code (In terms of performance), You may use a Dictionary to cache the results returned from GetAll method.