Copying the contents of a base class from a derived class

Question

I currently have a derived class and a base class. How can I make the base class of the derived class equal to a base class that I have? Will a shallow copy work?

Answer 1

I came up with a pretty good pattern for dealing with this situation.

public class Base
{
    public int BaseField;

    /// 

    /// Apply the state of the passed object to this object.       
    /// 
    public virtual void ApplyState(Base obj)
    {
        BaseField = obj.BaseField;
    }
}

public class Derived : Base
{
    public int DerivedField;

    public override void ApplyState(Base obj)
    {
        var src = srcObj as Derived;

        if (src != null)
        {
            DerivedField = src.DerivedField;
        }

        base.ApplyState(srcObj);        
    }
}

Given any two objects that share type 'Base', you can apply A to B or B to A.