in c#, is it possible to access the common protected fields of one child in another child class?

Question

See the question in code:

class commonParent {
     protected string name;
}

class child1:commonParent{
    // do some stuff
}

class child2:commonParent{
   // do some stuff

   protected void test(){
       child1 myChild1 = new child1();

       //is it possible to access myChild1.name in child2 without 
       //declaring the name public or internal?

      // I want to do something like this:
      string oldName = myChild1.name;

      //but I got the error:
      //Error   46  Cannot access protected member 'commonParent.name' 
      //via a qualifier of type 'child1'; the qualifier must be of 
      //type 'child2' (or derived from it)  
   }
}

The field "name" is only used by all children of commonParent class. I want to hide this field from outside (classes not derived from commonParent) while leaving it accessible within the scope of commonParent and its children.

Did it give any error when you tried to access myChild1.name? — Sachin Shanbhag, Oct 15 '11 at 07:57
Yes, I gor this error: Error 46 Cannot access protected member 'commonParent.name' via a qualifier of type 'child1'; the qualifier must be of type 'child2' (or derived from it) — LazNiko, Oct 15 '11 at 08:02

Damith · Accepted Answer · 2011-10-15T08:32:16.900

1

Read following blog post by Eric Lippert,

Why Can't I Access A Protected Member From A Derived Class?

try to use protected internal it will work

edited Oct 15 '11 at 08:32

answered Oct 15 '11 at 08:10

Damith

62,401
13
102
153

nice article, though it doesn't give any answer. it seems "protected internal" is lowest visibility i can set to get things done. – LazNiko Oct 15 '11 at 08:41

score 0 · Answer 2 · answered Jan 11 '15 at 01:08

My approach to this is to provide a protected static method that does have access to the protected value, but is only available to the derived classes, like in the code below:

class commonParent
{
    protected string name;

    protected static string GetName(commonParent other)
    {
        return other.name;
    }
}

class child1 : commonParent
{
    // do some stuff
}

class child2 : commonParent
{
    protected void test()
    {
        child1 myChild1 = new child1();
        string oldName = commonParent.GetName(myChild1);

    }
}

This has the benefit of providing access to protected data only to derived classes.

score 0 · Answer 3 · answered Oct 15 '11 at 07:57

0

you have to declare it at least protected

answered Oct 15 '11 at 07:57

Royi Namir

144,742
138
468
792

I know - he asked about the internal or public so i told him at least protected..... – Royi Namir Oct 15 '11 at 08:00

score 0 · Answer 4 · answered Oct 15 '11 at 08:01

0

I think this is bad design ,you should declare Name as Private and create a property with Get,Set accessors ,where you can chose if Get or Set could be Public ,Private or Protected ,otherwise Protected will allow any classes of the Same namespace to access a Field or Property .

answered Oct 15 '11 at 08:01

Rosmarine Popcorn

10,761
11
59
89

yeah I know that's the rule. but in my situation, the field "name" is only used by all children of commonParent class. I want to hide this field from outside but leaving it accessible within the scope of commonParent and its children. – LazNiko Oct 15 '11 at 08:08

score 0 · Answer 5 · answered Oct 15 '11 at 08:14

0

To answer your question, you can access them using reflection. This is not something you want to rely on, though.

answered Oct 15 '11 at 08:14

C.Evenhuis

25,996
2
58
72

in c#, is it possible to access the common protected fields of one child in another child class?

5 Answers5