Object type boxing with a reference type variable

Question

Boxing is when a value type is assigned to an object type. Is it the same when a reference type is assigned to an object?

When a type (which isn't object) is assigned, what happens? Is that boxing too?

    int num=5;
    object obj = num;  //boxing
    //////////////////////
    MyClass my = new MyClass();
    object obj = my; //what is name this convert  (whethere is boxing?)

Answer 1

Boxing is when a value type is assigned to an object type.

Close. "Boxing" happens when a value of value type is converted to a reference type.

Is it the same when a value of reference type is assigned to a variable of type object?

No. Boxing happens when a value of value type is converted to a reference type. Converting a value of reference type to object is not a boxing conversion, it is a reference conversion.

When a value of reference type (which isn't object) is assigned to a variable of type object, what happens?

A value of reference type is a reference. When a reference is assigned to a variable of type object, a copy of the reference is made in the storage location associated with the variable.

Is that boxing too?

No. Boxing happens when a value of value type is converted to a reference type. Converting a value of reference type to object is not a boxing conversion, it is a reference conversion.

Answer 2

I assume you mean something like

string s = "hello";
object x = s;        // no boxing, just implict conversion to base-type.

This works because System.String, like all other classes, derives from System.Object:

public sealed class String : Object { ... }