Return an Opaque object in C#

Question

I'm not very familiar with C# and I've not been able to find a reasonable answer anywhere. I simply want to return an object from a function that to the caller is opaque. I still want the user to be able to pass the object around, I just don't really want them calling any of the methods on the object.

In C++, you'd simply return a void* and then a function receiving that object would cast it to its appropriate type and call the methods on it.

public class Blob
{
    public void Method1() { do_something(); }
    public void Method2() { do_something_else(); }
}

public class BlobMaker
{
    public Blob CreateBlob() { return new Blob(); }  // This needs to return something opaque
}

public class BlobUser
{
    public void ConsumeBlob(var b)   // Method would take the opaque type
    {
        Blob newBlob = (Blob)b;
        b.Method1();
        b.Method2();
    }
}

public class MainApp
{
    BlobMaker m = new BlobMaker();
    var obj = m.CreateBlob();        //  obj returned by BlobMaker should be opaque.

    obj.Method1();                   //  This should not be allowed
    obj.Method2();                   //  This should not be allowed

    BlobUser user = new BlobUser();
    user.ConsumeBlob(obj);

}

In my case, I simply don't want to completely trust the user to have access to the Blob methods, so I want the object to be opaque. In the Win32 API this is done all the time with all sorts of Windows structures being opaque as void* pointers.

Now I know that you can use "unsafe" and probably do exactly the same thing in C#, but I was wondering if there was a better way in C# to do this?

** EDIT ** Just ignore me people.... I'm being a loony... the answer is simple. All that method has to do is return object instead of Blob and it done. Sorry people, it was a certified brain fart.