Is object a reference type or value type?

Question

I have still doubts about object. It is the primary base class of anything, any class. But is it reference type or value type. Or like which of these acts it? I need to get this clarified. I have difficulty understanding that.

     object obj1 = "OldString";      object obj2 = obj1;      obj1 = "NewString";      MessageBox.Show(obj1 + "   " + obj2);      //Output is  "NewString   OldString"  

In this case it acts like a value type. If object was reference type then why obj2 value is still "OldString"

   class SampleClass     {         public string Text { get; set; }     }      SampleClass Sample1 = new SampleClass();     Sample1.Text="OldText";               object refer1 = Sample1;     object refer2 = refer1;      Sample1.Text = "NewText";      MessageBox.Show((refer1 as SampleClass).Text +  (refer2 as SampleClass).Text);     //OutPut is "NewText   NewText"    

In this case it acts like reference type

We can deduce that object's type is what you box inside it. It can be both a reference type and value type. It is about what you box inside. Am I right?

Answer 1

It is a reference type

Doing an example with string isn't very illuminating, because string is also a reference type (as is SampleClass, obviously); your example contains zero "boxing".

if object is reference type then why obj2 value is still "OldString"

Why wouldn't it be? When you create a new string, that doesn't change old references to point at the new string. Consider:

 object obj1 = "OldString";  // create a new string; assign obj1 the reference to that new string "OldString"  object obj2 = obj1;  // copy the reference from obj1 and assign into obj2; obj2 now refers to  // the same string instance   obj1 = "NewString";  // create a new string and assign that new reference to obj1; note we haven't  // changed obj2 - that still points to the original string, "OldString"