无论是装箱还是拆箱？

Question

int i = 5;

string str = i.ToString();

String str1=(String) i.ToString();

As Int 's are value Type and String 's are reference Type

so Whether It is Boxing Or Unboxing ???

EDIT: Now For Second Statement Whether It is Boxing Or Unboxing ???

Answer 1

Your code is not an example of unboxing or boxing, but instead a method invocation of Int32.ToString() and assigning the return value to a string . The i.ToString() call doesn't assign an int to an object, but passes it to a method which returns a string . The second line with the (string) cast is superfluous and the C# compiler doesn't even emit it into IL.

For example, if you had this in a main method:

.method private hidebysig static 
    void Main (
        string[] args
    ) cil managed 
{
// Method begins at RVA 0x2050
// Code size 19 (0x13)
.maxstack 1
.entrypoint
.locals init (
    [0] int32 i
)

IL_0000: ldc.i4.5
IL_0001: stloc.0
IL_0002: ldloca.s i
IL_0004: call instance string [mscorlib]System.Int32::ToString()
IL_0009: pop
IL_000a: ldloca.s i
IL_000c: call instance string [mscorlib]System.Int32::ToString() // cast isn't here
IL_0011: pop
IL_0012: ret
} // end of method Program::Main

If you were boxing an integer:

int i = 1; 
object iBox = i; 

emits:

.locals init (
    [0] int32 i,
    [1] object o
)

IL_0000: nop
IL_0001: ldc.i4.5
IL_0002: stloc.0
IL_0003: ldloc.0
IL_0004: box [mscorlib]System.Int32
IL_0009: stloc.1
IL_000a: ret

Notice the box op code. If you aren't sure if something is boxing or unboxing, you can view the IL and see if this op code is there.

If you were unboxing an integer:

int j = (int) iBox;

The process is similar for other value types, like bool or double .

Answer 2

Boxing is the process of converting a value type to the type object or to any interface type implemented by this value type. Unboxing extracts the value type from the object. In this case it is neither boxing nor unboxing.

Answer 3

Boxing is the process of converting a value type to the type object or to any interface type implemented by this value type. When the CLR boxes a value type, it wraps the value inside a System.Object and stores it on the managed heap.

Unboxing extracts the value type from the object. Boxing is implicit; unboxing is explicit.

The concept of boxing and unboxing underlies the C# unified view of the type system in which a value of any type can be treated as an object.

In the following example, the integer variable i is boxed and assigned to object o.

C#

int i = 123;
// The following line boxes i. 
object o = i;  

The object o can then be unboxed and assigned to integer variable i:

C#

o = 123;
i = (int)o;  // unboxing

Answer 4

boxing is happened when you assign your data to object data type. since you are not doing this, there it is not boxing or unboxing.

Answer 5

装箱用于将值类型（字符串除外）转换为对象类型，使用ToString（）装箱方法装箱用于将对象类型转换为引用类型（字符串），使用anydatatype（字符串除外）.parse（）方法