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Seeking an explanation of how a "ReadOnlyCollection" works in this given case?

Posted on 2012-03-28
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Last Modified: 2012-03-28
I'm trying to find out what is happening in the following lines and I'm new to the "ReadyOnlyCollection." I was hoping someone could explain it to me. I'm especially confused about the line:

_children = new ReadOnlyCollection<Node>(_intChildren);
public Node Parent { get; }
private List<Node> _intChildren;
private ReadOnlyCollection<Node> _children;
public ReadOnly Collection<Node> Children
{
   get 
   {
      if (_children == null)
         _children = new ReadOnlyCollection<Node>(_intChildren);
      return _children;
   }
}

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Question by:Eindoofus
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2 Comments
 
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by:
käµfm³d   👽 earned 500 total points
ID: 37779658
A ReadOnlyCollection is just a wrapper around an existing collection. The thing that makes it "read only" is the fact that it does not expose an Add nor a Remove method. This, however, is just a facade, because if some piece of code already had access to the underlying list, then it could easily add to or remove from the collection.

This line:

_children = new ReadOnlyCollection<Node>(_intChildren);

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is just initializing the private member variable _children with a new instance of a ReadOnlyCollection--one which wraps the private member variable _intChildren. Other parts of the class containing this code would be free to modify the underlying list (in this case:  _intChildren) since it is a member variable and thus scoped to the entire class. Outside code, however, cannot modify the list because it is private and the only public interaction with this list is by way of the Children property, which points to the ReadOnlyCollection wrapper.
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Author Closing Comment

by:Eindoofus
ID: 37779764
Thanks :)
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