Question

I have a class called FieldDesc.

public class FieldDesc {
    public FieldDesc() {
    }
}

I also have another class that inherits from FieldDesc called StandardHoursByCommunitySvcType.

public class StandardHoursByCommunitySvcType: FieldDesc {
    public StandardHoursByCommunitySvcType() {
    }
}

In my control I have –

FieldDesc aTable;
aTable = new FieldDesc();

String TableName = "StandardHoursByCommunitySvcType";

What do I have to do to get aTable to know that it is an object of type StandardHoursByCommunitySvcType ?

Answer 1

If you have the two classes

public class FieldDesc
{
    public FieldDesc()
    {
    }

    public void A()
    {
    }

    public virtual void V()
    {
        Console.WriteLine("V from FieldDesc");
    }
}

public class StandardHoursByCommunitySvcType : FieldDesc
{
    public StandardHoursByCommunitySvcType()
    {
    }

    public void B()
    {
    }

    public overrides void V()
    {
        Console.WriteLine("V from StandardHoursByCommunitySvcType");
    }
}

You can do this

FieldDesc fd = new StandardHoursByCommunitySvcType();
StandardHoursByCommunitySvcType svc = new StandardHoursByCommunitySvcType();

fd.A(); // OK
fd.B(); // Fails (does not compile)
((StandardHoursByCommunitySvcType)fd).B(); // OK
fd.V(); // OK, prints "V from StandardHoursByCommunitySvcType"

svc.A(); // OK
svc.B(); // OK
svc.V(); // OK, prints "V from StandardHoursByCommunitySvcType"

The derived class is assignment compatible to the base class; however, accessed through a variable typed as the base class you will only see the the members of the base class.