C# Public vs. Internal in different assemblies

Question

I am little bit confused.

I know that public is accessible from anywhere and internal classes are accessible only within the assembly.

But I found something strange in my code.

I've got three projects in one solution. All projects shares the same namespace.

Project A (main executable)

namespace Everything 
{
   class Program 
   {
      void Main() 
      {
         Runner r = new();
      }
   }
}

Project B (library class)

namespace Everything 
{
   public class Runner 
   {
      public Runner() 
      {
         // Loads external assembly in runtime and creates instance
         Assembly assembly = Assembly.Load("my.dll","my.pdb");
         Type type = assembly.GetType("Everything.InternalClass");
         Execute Instance = (Execute)Activator.CreateInstance(type);
      }
   }

   public class Execute
   {
       //something to do
   }
}

And finally Project C (my.dll) (another class library)

namespace Everything 
{
   class InternalClass : Execute
   {
      // This is executed in correct way - even it is in different assembly and it is set as internal (by default)
   }
}

Why this is working properly? I was thinking, that I need to use public in my Project C - becuase it is in different assembly...

yea, car cannot be started without key, but if you are gonna strip some wires and bypass the key, well.. — Mat J, Jul 20 '21 at 07:20
So, the reason is as Joey stated in the comment below, that the reflection bypasses the accessibility modifiers? — Josef Širůčka, Jul 20 '21 at 07:44
Accessibility modifiers are primarily there for _compile-time_ safety. When you use reflection, the guardrails are gone. See duplicate. — Peter Duniho, Jul 20 '21 at 17:10

score 2 · Accepted Answer · answered Jul 20 '21 at 07:20

Accessibility modifiers affect where types and members are visible from normal C# code. Reflection allows you to bypass all that. You can also set private fields via reflection and more.

If you want a normal C# way to access internal types, you can use the InternalsVisibleTo attribute.

score 1 · Answer 2 · answered Jul 20 '21 at 07:23

1

The GetType returns everything you search for. If you want to get the public members, use GetExportedTypes instead. With reflection you can see and use all members.

answered Jul 20 '21 at 07:23

alexrait

407
3
15

C# Public vs. Internal in different assemblies

2 Answers2