动态将派生类类型转换为基类C＃

Question

public DerivedClass : BaseClass
{
   // code
}

DerivedClass B = (DerivedClass)MethodReturnsBaseClassObject();
B.DoWork();  

There are many Derived classes being inherited from BaseClass . So everytime i need to write a new method to use some of the properties.

Is this possible that using reflection we make DerivedClass type dynamic and do something like this and make it generic.

System.Type type = GetRequestFromSession().GetType();
type B = (type )MethodReturnsBaseClassObject();
Console.WriteLine( B.Name);  
Console.WriteLine( B.Age);  

any help is appreciated.

Answer 1

You can have safe access to members of the derived type (without casts) while enforcing the base class constraint if you employ a generic method with the following signature:

public TDerived MethodReturnsDerivedObject<TDerived>()
    where TDerived : BaseClass

Your calls will then look like this:

DerivedClass b = MethodReturnsDerivedObject<DerviedClass>();

b.ExecuteSomeMethodDefinedInBaseClass();

Console.WriteLine(b.SomePropertyDefinedInDerivedClass);  

Answer 2

This feels like bad design to me: you make something generic that you use as something that isn't. Maybe you should rethink your design.

For what your question is concerned, maybe you can create a proxy method or class that returns the type you expect. This is only useful when there is a low number of methods you call.

Another option is to use the dynamic keyword, but I would advice only to use that if nothing else works.

Answer 3

I would go with Kirill Shlenskiy's answer for now. But I'd also like to suggest moving this method onto the base class itself if it makes sense to do so . There may be tangled dependencies or other weirdness that prohibits this solution, but it may also allow you to have one consumer without using generics.