Compiler Error C2847

cannot apply sizeof to managed or WinRT type 'class'

The sizeof operator gets the value of an object at compile time. The size of a managed or WinRT class, interface, or value type is dynamic and so cannot be known at compile time.

For example, the following sample generates C2847:

// C2847.cpp
// compile with: /clr
ref class A {};

int main() {
   A ^ xA = gcnew A;
   sizeof(*xA);   // C2847 cannot use sizeof on managed object
}