C# trying to assign a class to another class

Question

I am trying to run the following code :

classA = classD;

to assign the values in classA to classD (the variable is being shared from another class called 'classC').

the above line would normally work in C++ but in C# its returning an error! is this possible in C#?

How are `classA` and `classD` related? What's the inheritance chain? — Oded, Dec 11 '11 at 14:44
`class D : C` and `class A : D` so a variable is being copied from C to D and then from D to A. — Ahoura Ghotbi, Dec 11 '11 at 14:45
@AhouraGhotbi so you want to copy a variable from class D to class A — Glory Raj, Dec 11 '11 at 14:48
yes but I was instructed to copy the classes and not the variables — Ahoura Ghotbi, Dec 11 '11 at 14:49
I was told that in C++ you can do the following : `classA = classB` and it will copy whatever variable they have in common. so I am not really sure — Ahoura Ghotbi, Dec 11 '11 at 14:52
possible duplicate of http://stackoverflow.com/questions/1031023/copy-a-class-c-sharp — Glory Raj, Dec 11 '11 at 14:54
I think we need to see more code to put context to this question so someone can give you an appropriate answer. Also, it's possible your instructor just meant copy the class properties from one object to another. — danludwig, Dec 11 '11 at 14:59

Marc Gravell · Accepted Answer · 2011-12-11T15:26:03.927

From the comments A : D, so all A are D, but not all D are necessarily A.

So with two variables:

A classA;
D classD = ...

We need

classA = (A) classD;

This does a type-check, to confirm that the specific classD is actually also an A. If this is the case (or it is null) then the assignment is successful; otherwise an exception occurs.

This is to prevent you assigning something to classA that is actually not really an A.

Note it is implicit the other way, since the compiler knows it to be valid:

classD = classA; // always valid - no type check

score 0 · Answer 2 · answered Dec 11 '11 at 15:03

If you are asking can you copy attributes of the same name from instances of different classes, then no.

Saying classA = classB where the classes are not related in the class hierarchy will cause a type error. If they are related, then all you are doing is changing the value of the variable classA, not copying anything.

C# trying to assign a class to another class

2 Answers2