Are value types wrapped in reference types allocated on Stack or Heap?

class ClassA // ClassA is allocated on heap
    {

        public int intTest; // Is intTest also allocated on heap??
        public String strTest; // Where is strTest allocated..stack or heap??

        public ClassA()
        {
            intTest = 1;
            strTest = "First";
        }

    }

    class ClassB
    {


        public void fnClassB()
        {
            ClassA A = new ClassA();

            ClassA Aa = new ClassA();

            Console.WriteLine(A.intTest);
            Console.WriteLine(A.strTest);

            fnChangeValue(A,Aa.intTest,Aa.strTest);

            Console.WriteLine(A.intTest); //A.intTest gives the new value since A is allocated on heap.

            Console.WriteLine(A.strTest);

            Console.WriteLine(Aa.intTest); 

            Console.WriteLine(Aa.strTest); //Aa.strTest does not give the value modified in the function, though strTest is a string variable allocated on heap...Why is this...?


        }

        void fnChangeValue(ClassA A, int intTest, String strTest)
        {
            A.intTest = 2;

            A.strTest = "Second";

            intTest = 3;

            strTest = "Third";
        }
    }

Output of the above program is :

1
First
2
Second
1
First