c# - Implementing IEnumerable for Leaf Nodes of Composite Pattern -

i've implemented composite pattern follows

public interface icomponent {    string name { get; } }  public interface icomposite : icomponent {     void addrange(ienumerable<icomponent> components); } public interface ileaf : icomponent {     string content { get; }     string parent { get; } }  public class composite : icomposite {     // return iterator?     private readonly list<icomponent> _children = new list<icomponent>();      public composite(string name)     {         name = name;     }      public string name { get; }      public void addrange(ienumerable<icomponent> components)     {         _children.addrange(components);     } }  public class leaf : ileaf {     public string name { get; }     public string content { get; }     public string parent { get; }      public leaf(string name, string content, string parent)     {         name = name;         content = content;         parent = parent;     } } 

i've populated composite xml file follows

var collection = xelement.load(@"c:\somexml.xml");    var composite = createcomposite(collection); 

where

public icomponent createcomposite(xelement element)     {         if (!element.haselements)             return new leaf(element.name.localname, element.value, element.parent.name.localname);          var composite = new composite(element.name.localname);         composite.addrange(element.elements().select(createcomposite));         return composite;     } 

this populates composite expected - great! however, i'd composite return iterator via implementation of ienumerable. tried this

public class composite : icomposite, ienumerable<icomponent> {     // return iterator?     private readonly list<icomponent> _children = new list<icomponent>();      public composite(string name)     {         name = name;     }      public string name { get; }      public void addrange(ienumerable<icomponent> components)     {         _children.addrange(components);     }      ienumerator ienumerable.getenumerator()     {         return getenumerator();     }      public ienumerator<icomponent> getenumerator()     {         foreach (var child in _children)         {             yield return child;         }     } } 

but iterates through top level of components, i.e., components nested within _children not returned. how update recursively iterate through components?

you can iterate recursively (it iteration in depth-first manner):

public interface icomposite : icomponent, ienumerable<icomponent> {     void addrange(ienumerable<icomponent> components); }  public ienumerator<icomponent> getenumerator() {     foreach (var child in _children)     {         yield return child;         var composite = child icomposite;         if (composite != null) {             foreach (var sub in composite) {                 yield return sub;             }         }      } } 

if want avoid cast icomposite - need redesign interfaces , make composite hold list of icomposites instead of components. ileft become icomposite dummy implementation.