Boxing conversions

A boxing conversion permits any value-type to be implicitly converted to the type object or to any interface-type implemented by the value-type. Boxing a value of a value-type consists of allocating an object instance and copying the value-type value into that instance.
The actual process of boxing a value of a value-type is best explained by imagining the existence of a boxing class for that type. [Example: For any value-type T, the boxing class behaves as if it were declared as follows: sealed class T_Box { T value; public T_Box(T t) { value = t; } }
Boxing of a value v of type T now consists of executing the expression new T_Box(v), and returning the resulting instance as a value of type object. Thus, the statements int i = 123; object box = i; conceptually correspond to int i = 123; object box = new int_Box(i); end example]
Boxing classes like T_Box and int_Box above don't actually exist and the dynamic type of a boxed value isn't actually a class type. Instead, a boxed value of type T has the dynamic type T, and a dynamic type check using the is operator can simply reference type T. [Example: For example, int i = 123; object box = i; if (box is int) { Console.Write("Box contains an int"); } will output the string "Box contains an int" on the console. end example]
A boxing conversion implies making a copy of the value being boxed. This is different from a conversion of a reference-type to type object, in which the value continues to reference the same instance and simply is regarded as the less derived type object. [Example: For example, given the declaration struct Point { public int x, y; public Point(int x, int y) { this.x = x; this.y = y; } } the following statements Point p = new Point(10, 10); object box = p; p.x = 20; Console.Write(((Point)box).x); will output the value 10 on the console because the implicit boxing operation that occurs in the assignment of p to box causes the value of p to be copied. Had Point been declared a class instead, the value 20 would be output because p and box would reference the same instance. end example]