The role of assigning Null to a reference in C #

There are Class A, and variables A and B of type A. After initialization of a, assign a to B. The A is then assigned null. B can still be used after that.

Thinking error: After thought A=null, B should also be equal to NULL.

The actual test results are as follows

    classProgram {Static voidMain (string[] args) {            Try{A A=NewA () {data ="Hello World" }; A b=A; if(B.equals (a)) {Console.WriteLine ("A and B are the same object"); }                Else{Console.WriteLine ("A and B are not of the same object"); } a.data="Good Morning"; A=NULL; //B = null;GC.                Collect ();            Console.WriteLine (B.data); }            Catch(Exception ex) {Console.WriteLine (ex).            Message);        } console.readkey (); }    }    classA {Internal stringdata; }

Finally found the answer on the StackOverflow, the original to a reference is null, just the point is removed. Other variables can also point to previous content

Http://stackoverflow.com/questions/8069396/setting-a-type-reference-type-to-null-doesnt-affect-copied-type

The role of assigning Null to a reference in C #