C#

1. You want polymorphic behaviour, but the base class doesn't know what that might be. This is what abstract methods are for.
2. You want to allow subclasses to provide behaviour, but the base class has some idea what it a sensible default. For this you should use a virtual method, even if the default action is nothing.
   

   public virtual void Walk(){}

3. You know what the basic template for behaviour is, but you want subclasses to be able to customise parts of it, or you are missing information. I tend to do this with the 'MethodName'/'MethodNameInner' approach, where MethodNameInner is usually protected abstract, but if there is a reasonable default (often empty), it can be protected virtual instead.
   

   public void Walk(){
    Leg legToMove = LegToWalkWith;
    legToMove.MoveForward();
   }
   
   protected abstract Leg LegToWalkWith { get; }

   
   
   or more realistically (pseudocode as I can't remember exactly how this works right now):
   
   

   public void ReadConfig(string configFile){
    XmlDocument xmlDoc = GetXmlDocument(configFile); // don't worry about this
    XmlElement elem = xmlDoc.GetElement(ConfigNodeXpath);
    foreach(XmlNode node in elem.ChildNodes){
     XmlElement subelem = node as XmlElement;
     if(subelem == null) continue;
     // ... etc, e.g. set property by reflection
    }
   }
   
   protected abstract string ConfigNodeXpath { get; }

   
   

Xarzu wrote:

It seems that once the databinding is done, and if you change the data you have
to rebind to the control.