Cannot access a non-static member of outer type via nested type

Question

I have error

Cannot access a non-static member of outer type 'Project.Neuro' via nested type 'Project.Neuro.Net'

with code like this (simplified):

class Neuro
{
    public class Net
    {
        public void SomeMethod()
        {
            int x = OtherMethod(); // error is here
        }
    }

    public int OtherMethod() // its outside Neuro.Net class
    {
        return 123;  
    }
}

I can move problematic method to Neuro.Net class, but I need this method outside.

Im kind of objective programming newbie.

Thanks in advance.

Answer 1

The problem is that nested classes are not derived classes, so the methods in the outer class are not inherited.

Some options are

1. Make the method static:

   class Neuro
   {
       public class Net
       {
           public void SomeMethod()
           {
               int x = Neuro.OtherMethod(); 
           }
       }
   
       public static int OtherMethod() 
       {
           return 123;  
       }
   }
   

2. Use inheritance instead of nesting classes:

   public class Neuro  // Neuro has to be public in order to have a public class inherit from it.
   {
       public static int OtherMethod() 
       {
           return 123;  
       }
   }
   
   public class Net : Neuro
   {
       public void SomeMethod()
       {
           int x = OtherMethod(); 
       }
   }
   

3. Create an instance of Neuro:

   class Neuro
   {
       public class Net
       {
           public void SomeMethod()
           {
               Neuro n = new Neuro();
               int x = n.OtherMethod(); 
           }
       }
   
       public int OtherMethod() 
       {
           return 123;  
       }
   }
   

Answer 2

you need to instantiate an object of type Neuro somewhere in your code and call OtherMethod on it, since OtherMethod is not a static method. Whether you create this object inside of SomeMethod, or pass it as an argument to it is up to you. Something like:

// somewhere in the code
var neuroObject = new Neuro();

// inside SomeMethod()
int x = neuroObject.OtherMethod();

alternatively, you can make OtherMethod static, which will allow you to call it from SomeMethod as you currently are.