This is part two of a three part series on working with master-detail data.  In part one I showed how to present detail values on the master using a utility I wrote called the SubAttributeAccessor.  In this article I will go into detail as to how the SubAttributeAccessor works. In part three, I’ll introduce a descendant of DataGridViewColumn that will allow us to show the indexed detail data in line with the master data as additional columns.

The SubAttributeAccessor is a class that when added to a parent class is able to present a list of children as an indexed property of the parent.  For example, let’s imagine that we had a class called song and that is has among other properties one that is a list of attribute objects.

public class Song {
    public List<Attribute> Attributes {get; set;}
}

public class Attribute {
    public string Key {get; set;}
    public byte[] Value {get; set;}
}

These two classes form the basis of the imaginary scenario that I used in part one of this article.  A song can have an unlimited number of attributes.  As things stand, we can add an attribute to a song like so:

Song mySong = new Song();
Attribute myAttribute = new Attribute();
myAttribute.Key = "Tempo";
myAttribute.Value = "slow";
mySong.Attributes.Add(myAttribute);

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