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I have class placed on the data layer, and it is initially instantiated with basic information.
It exposes a sub object called ExternalSourceData (or a method called Enrich), that calls an external source (consumes time) and instantiates some more data members inside the same object.

Clarification: I haven't used inheritance since this object is exposed to an external project, that uses it as an external assembly. Moreover, I want to clearly differ between the "regular" data members and the "external data source" members.

Thus, that's what I came up with:
List list = new List();
ExposedClass a = new ExposedClass(list); // a has members such as size, date
int size = a.size;
string name =;

if (LoadFromExternal)
   a.ExternalSourcedData = new ExternalSourceData(externalSourceSessionParms)

and the usage will be:
if (a.ExternalSourcedData != null){
   Guid id = a.ExternalSourcedData.ID;

I want the ExternalSourcedData ctor to use the list passed to a (it also passes over the elements of the list). unfortunately, from what i gather, there's no way to do it on c# (on c++ it would be called "Friend" and in java it could have been solved by using an inner class).

Is anyone familiar with a solution to that problem ? Maybe a design pattern that would make it more acceptable as i don't want to pass the list again to the ExternalSourceData ctor?

Thanks allot.
Updated 2-Mar-11 22:44pm

1 solution

You just need to add a public method for invoking the event. Microsoft already does this for some events such as PerformClick for controls that expose a Click event.

public class CustomGUIElement
    public void PerformClick()

    protected virtual void OnClick(EventArgs e)
        if (Click != null)
            Click(this, e);
You would then do the following inside your example event handler...

public void CustomForm_Click(object sender, MouseEventArgs e)
OrenSchwartz 3-Mar-11 5:05am
Hi thanks !

how would registering to an event help ?
if the assembly user registers to the event, all he'll know is when the enrichment occurred. he would still have to pass the "inner class" the list that i already passed the father.

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