C# Reference and Value Type Examples

            //Create an instance of a class and a structure
           //(definitions for these classes are not shown in this source code)
            SpangeClass spangeClassOne = new SpangeClass(); //reference type
            SpangeStruct spangeStructOne = new SpangeStruct(); //value type

           //set fields
            spangeClassOne.FirstName = "Andrew";
           spangeClassOne.LastName = "Strauss";
           spangeStructOne.FirstName = "Graeme";
           spangeStructOne.LastName = "Swann";

           //return all fields
            MessageBox.Show(string.Format("{0} {1} and {2} {3}",
               spangeClassOne.FirstName,
               spangeClassOne.LastName,
               spangeStructOne.FirstName,
               spangeStructOne.LastName));
          
           //make copies of both
            SpangeClass spangeClassTwo = spangeClassOne;
           SpangeStruct spangeStructTwo = spangeStructOne;

           //set fields on copies to show how
           //fields on the class (reference type) will update the original where as
           //fields on the struct (value type) will not update the original
            spangeClassTwo.FirstName = "Ricky"; //this updates the original as well (reference type)
            spangeClassTwo.LastName = "Ponting";//Because second instance of the class is given a new area
                                                   //of the heap but not a new area of the stack.
                                               //Both bits of heaps are pointing at the same bit of stack
            spangeStructTwo.FirstName = "Nathan"; //this does not update the original as well (value type)
            spangeStructTwo.LastName = "Hauritz"; //Because both structs are in seperate areas of the stack

           MessageBox.Show(string.Format("{0} {1} (changed - reference type) and {2} " +
                                                   "{3} (did not change - value type)",
               spangeClassOne.FirstName,
               spangeClassOne.LastName,
               spangeStructOne.FirstName,
               spangeStructOne.LastName));

           //a simpler example with an array (reference) and ints (value)

           //originals
            string[] TestArray = new string[10];
           TestArray[1] = "Original Array Value";
           int TestInt = 99;

           //copies
           //Array update will alter the original where as
           //int update will only alter the copy and not the original, so we don't see 42
            string[] TestArrayCopy = TestArray;
           TestArrayCopy[1] = "New Array Value"; //this updates the original as well (reference type)
            int TestIntCopy = TestInt;
           TestIntCopy = 42; //this does not update the original as well (value type)

           MessageBox.Show(TestArray[1]);
           MessageBox.Show(TestInt.ToString());