Are reference types always stored on the stack?.

No, reference types in C# are not always placed on the stack. Reference types are usually allocated on the managed heap, and only a reference to the object is stored on the stack.

For example:

class MyClass { }

void Method()
{
    MyClass obj = new MyClass(); // obj is a reference stored on the stack
    // The MyClass object itself is allocated on the heap
}

Value types, such as structures (struct), are typically stored on the stack if they are local variables, but they can also be stored on the heap if they are fields of reference objects.

Thus, placement depends on the type and the context of use, not only on whether the type is a reference type.