將泛型類型轉換爲子類型

Question

我以泛型類型開始，並且堅持使用我的項目。也許我不太瞭解泛型。解釋已經插入。基本上，我需要實現DO（）方法，但我不知道如何解決<T2>：

public abstract class MyGenericClass<T> { } 

    public class MyGenericClass<T, T2> : MyGenericClass<T> 
    { 
     public Expression<Func<T, T2>> expression; 

     public MyGenericClass(Expression<Func<T, T2>> expression) 
     { 
      this.expression = expression; 
     } 
    } 

    public class MyClass<T> 
    { 
     // I need to mantain a list of my generic class for later use. 
     // I don't know T2 at this point. 
     // So I Chose to use Inheritance as a workaround (MyGenericClass<T> and MyGenericClass<T, T2>). 
     // Maybe it's not a good solution but I counldn't find out other solution. 
     public List<MyGenericClass<T>> MyGenericList = new List<MyGenericClass<T>>(); 

     // I receive the parametric argument T2 here as part of an Expresion. 
     // And I keep the expression in my list. 
     public MyGenericClass<T, T2> ReceivingMethod<T2>(Expression<Func<T, T2>> expression) 
     { 
      MyGenericClass<T, T2> genericImp = new MyGenericClass<T, T2>(expression); 
      MyGenericList.Add(genericImp); 
      return genericImp; 
     } 
    } 

    public class Client<T> 
    { 
     MyClass<T> class1; 

     // class1 has been created and his field MyGenericList has beed populated. 
     // Then when I call Do().... 
     public void Do() 
     { 
      foreach (var item in class1.MyGenericList) 
      { 
       // ...I need something like this here, 
       // but it does not compile because I don't know T2 here. 
       // The caller of Do() method doesn't know T2. 
       MyGenericClass<T, T2> myGenericItem = (MyGenericClass<T, T2>)item; 
       var a = myGenericItem.expression; 
      } 

     } 
    }