在私有类型上动态抛出Microsoft.CSharp.RuntimeBinder.RuntimeBinderException

Question

I need to write some code to clone a HashSet of any type but the type is not known beforehand. Due to the lack of a non generic interface (unlike dictionary there is no ISet interface just a ISet<>) I have to use reflection. I decided to let dynamic handle the reflection work for me but now iam running into a seemingly very weird problem when I run the following code (heavily simplified from the real world code):

class Program
{
    static void Main(string[] args)
    {
        HashSet<ReferenceType> source = new HashSet<ReferenceType>();
        ExtMethodsCloning.DeepClone(source);
    }

    private class ReferenceType { }
}

public static class ExtMethodsCloning
{
    public static void SomeCloningMethodThatHappensToCallClear(dynamic baseObj)
    {
        baseObj.Clear();
    }
}

If you move DeepClone to the program class or make ReferenceType public it works. It somehow needs to see ReferenceType in order to work. Even though we are only interested in calling the Clear method which isnt even defined on ReferenceType but on HashSet<>.

How can I workaround this while not having to resort to manually doing the reflection work? Remember the type is not know at compile time so no generics.

EDIT: iam aware of the fact that at some point I would have to create new instances and thus have to call private constructors. If its even possible to call a constructor using dynamic I would expect an error in that case (and workaround it by using reflection) but not now when just calling Clear on the HashSet.

Answer 1

I don't understand the need for dynamic here. I'm pretty sure you can do what you need with generics.

EDIT: How to call a generic method by reflection:

 static void Main(string[] args)
 {
     var hs1 = new HashSet<SomePrivateClass>();
     CallClear(hs1);
 }

 public static void CallClear(object objectThatIsAHashSet)
 {
     var method = typeof(Program).GetMethod("Clear", BindingFlags.Public | BindingFlags.Static);
     var hsGenericType = objectThatIsAHashSet.GetType().GetGenericArguments()[0];
     var genericMethod = method.MakeGenericMethod(hsGenericType);
     genericMethod.Invoke(null, new[] {objectThatIsAHashSet});
 }

private class SomePrivateClass { }

public static void Clear<T>(HashSet<T> hs)
{
    hs.Clear();
}

EDIT 2: Why doesn't it work with dynamic.

Basically, dynamic only allows access to public members of a type. As such, it cannot be used to call either a private member, or a private type. The basic rule is that if you could not refer to a method in a piece of code using it's type, you cannot access it using dynamic (ie you can't use dynamic to break encapsulation).