Object passed as parameter to another class by value or reference

Question

In C   I know that by default  any parameters passed into a function would be by copy  that s  within the function  there is a local copy of the parameter  But  what about when an object is passed as parameter to another class    Would a scenario like the following one be passed by reference or by value   class MyClass      private Object localObj      public void SetObject Object obj          localObj   obj          void Main        Object someTestObj   new Object       someTestObj name    My Name      MyClass cls   New MyClass       cls SetObject someTesetObj       In this case  would the class variable localObj be having the same copy as the someTestObj created in the Main driver class  Or would the two variables be pointing to a different object instance

User · Answer

An Object if passed as a value type then changes made to the members of the object inside the method are impacted outside the method also                  But if the object itself is set to another object or reinitialized then it will not be reflected outside the method  So i would say object as a whole is passed as Valuetype only but object members are still reference type           private void button1 Click object sender  EventArgs e                Class1 objc            objc   new Class1            objc empName    name1           checkobj  objc           MessageBox Show objc empName      propert value changed  but object itself did not change           private void checkobj   Class1 objc                objc empName    name 2           Class1 objD   new Class1            objD empName   name 3           objc   objD           MessageBox Show objc empName      name 3

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Assuming someTestObj is a class and not a struct  the object is passed by reference  which means that both obj and someTestObj refer to the same object   E g  changing name in one will change it in the other   However  unlike if you passed it using the ref keyword  setting obj   somethingElse will not change someTestObj

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In general  an  object  is an instance of a class  which is an  image   fingerprint  of a class created in memory  via New keyword   The variable of object type refers to this memory location  that is  it essentially contains the address in memory  So a parameter of object type passes a reference  link  to an object  not a copy of the whole object

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Objects  are NEVER passed in C  --  objects  are not values in the language  The only types in the language are primitive types  struct types  etc  and reference types  No  object types    The types Object  MyClass  etc  are reference types  Their values are  references  -- pointers to objects  Objects can only be manipulated through references -- when you do new on them  you get a reference  the   operator operates on a reference  etc  There is no way to get a variable whose value  is  an object  because there are no object types   All types  including reference types  can be passed by value or by reference  A parameter is passed by reference if it has a keyword like ref or out  The SetObject method s obj parameter  which is of a reference type  does not have such a keyword  so it is passed by value -- the reference is passed by value

User · Answer

If you need to copy object please refer to object cloning  because objects are passed by reference  which is good for performance by the way  object creation is expensive   Here is article to refer to  Deep cloning objects

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I found the other examples unclear  so I did my own test which confirmed that a class instance is passed by reference and as such actions done to the class will affect the source instance   In other words  my Increment method modifies its parameter myClass everytime its called   class Program       static void Main string   args                MyClass myClass   new MyClass            Console WriteLine myClass Value       Displays 1         Increment myClass           Console WriteLine myClass Value       Displays 2         Increment myClass           Console WriteLine myClass Value       Displays 3                    Increment myClass           Console WriteLine myClass Value       Displays 4         Console WriteLine  Hit Enter to exit             Console ReadLine               public static void Increment MyClass myClassRef                myClassRef Value             public class MyClass       public int Value  get set       public MyClass                 Value   1

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Objects will be passed by reference irrespective of within methods of same class or another class  Here is a modified version of same sample code to help you understand  The value will be changed to  xyz    using System  using System Collections Generic  using System Diagnostics  using System Linq  using System Text   namespace ConsoleApplication1       public class Employee               public string Name   get  set               public class MyClass               public Employee EmpObj           public void SetObject Employee obj                        EmpObj   obj                       public class Program              static void Main string   args                        Employee someTestObj   new Employee                someTestObj Name    ABC                MyClass cls   new MyClass                cls SetObject someTestObj                Console WriteLine  Changing Emp Name To xyz                someTestObj Name    xyz                Console WriteLine  Accessing Assigned Emp Name                Console WriteLine cls EmpObj Name                Console ReadLine

[c#] Object passed as parameter to another class, by value or reference?

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