Simple scope question

[bobneedshelp]

I come from a Java background so this a puzzle to me. I'm wondering why this happens in .net. Why do I have use the class name in order to get the variables value in .net?

Public Class Form1
    Public varPub as String = "PUBLIC"
    Private Sub Main
        varPub = "PUBLIC"
        subClass = New SecondClass()
        subClass.IsIT()
    End Sub
End Class
 
Public Class SecondClass
    Inherits Form1
    Public Sub IsIT()
        MessageBox.Show(varPub) 'Shows blank
        MessageBox.Show(Form1.varPub) 'shows value
    End Sub
End Class
 

[mmaslar]

In your "SecondClass" class, varPub is not defined. (In fact, there ought to be a warning to that effect on MessageBox.Show(varPub).

So, it's necessary to specify the class where the variable is actually defined.

[Plater]

You went from java to vbnet? I would have thought c# was the natural transition for a java person.

At any rate that is interesting that a derived class does not get the default value of the base class. Hmm

I think you doctored your source code(possibly to make it be an "example") when you copied it over, because the C# version of that doesn't even compile.

[Curtis Rutland]

Well, part of the problem is the way VB.NET likes to hold people's hands, trying to make it easy for you, but instead making it easy to misunderstand and make mistakes.

Technically, you shouldn't be able to call Form1.varPub in SecondClass. The only way you should be able to do that is if it were declared as Shared (static). What VB is doing for you is creating an instance of Form1 and getting the public member varPub for you.

As to the other side of the problem, I'm not too sure. I put together a sample C# version of your program to test your problem, and it works fine for me.

public class Program
{
    public string varPub = "PUBLIC";
 
    static void Main(string[] args)
    {
        subClass c = new subClass();
        c.IsIT();
        Console.ReadKey();
    }
}
 
public class subClass : Program
{
    public void IsIT()
    {
        Console.WriteLine(varPub);
    }
}
 

[Curtis Rutland]

In your "SecondClass" class, varPub is not defined. (In fact, there ought to be a warning to that effect on MessageBox.Show(varPub).

So, it's necessary to specify the class where the variable is actually defined.

That shouldn't be right, because his SecondClass inherits Form1. It should inherit all it's members and methods as well.

EDIT:
I know that's not correct, because I just put this test together in VB.NET:

Module Module1
 
    Sub Main()
        Dim c As New Class2
        c.IsIT()
        Console.ReadKey()
    End Sub
 
End Module
 
Public Class Class1
    Public varPub As String = "PUBLIC"
End Class
 
Public Class Class2
    Inherits Class1
    Public Sub IsIT()
        Console.WriteLine(varPub)
    End Sub
End Class
 

And it works like expected. I'm not quite sure what's wrong with OP's code. I'd try to imitate it, but it seems like a strange combination of a console app and a windows forms app.

Can you clarify what you are doing?

[bobneedshelp]

That shouldn't be right, because his SecondClass inherits Form1. It should inherit all it's members and methods as well.

EDIT:
I know that's not correct, because I just put this test together in VB.NET:

Module Module1
 
    Sub Main()
        Dim c As New Class2
        c.IsIT()
        Console.ReadKey()
    End Sub
 
End Module
 
Public Class Class1
    Public varPub As String = "PUBLIC"
End Class
 
Public Class Class2
    Inherits Class1
    Public Sub IsIT()
        Console.WriteLine(varPub)
    End Sub
End Class
 

And it works like expected. I'm not quite sure what's wrong with OP's code. I'd try to imitate it, but it seems like a strange combination of a console app and a windows forms app.

Can you clarify what you are doing?

C# was my choice but the boss said vb. The setup is a generic service form calling a class
to run applicaitons.

I have several applications that use the same fields to insert data into a database. I created a separate class to do this. The initial idea was to pass a structure and that
didn't work at all. It would be easier on the eyes to see the structure passed and then manipulate the data instead of passing ten variables. The function gets called multiple times.

The next step was to get the variable information from the original class. I thought you could inherit a class and access the variables the same way you could in java. At least that's what my vb book says. I added this to my test application to see how to get the data over. The only way to do it was to add the class name in front of the variable.

[Plater]

I did the following:

secondclass cd = new secondclass();
cd.testit(); 
 

public class baseclass
{
    protected string somestr = "INIT VALUE";
 
    public baseclass()
    {
      somestr = "baseclass constructor";
    }
}
public class secondclass : baseclass
{
    public void testit()
    {
      System.Windows.Forms.MessageBox.Show(somestr);
    }
}
 

And the output was "baseclass constructor", so even in an inherited class, the base class's constructor is called. If that helps at all.
I had to declare the member variable as "protected" to keep it hidden(not public) but to allow it to be visible to the derrived class.

[bobneedshelp]

That works for me in an application but for some reason not in a service. I am using a namespace for the service and those seem to affect how variables can be accessed. The fix was making the variable shared. I'll try to figure out why later but it's working now.

Thanks for the help.

[Plater]

Oooo some of those terms public/private/static/protected/internal and etc effect if a class with another namespace (and/or different "assembly") can access the member.
I don't know much about using them in "fancy" ways