Accessing a struct collection property from within another collection
- by paddyb
I have a struct that I need to store in a collection. The struct has a property that returns a Dictionary.
public struct Item
{
private IDictionary<string, string> values;
public IDictionary<string, string> Values
{
get
{
return this.values ?? (this.values = new Dictionary<string, string>());
}
}
}
public class ItemCollection : Collection<Item> {}
When testing I've found that if I add the item to the collection and then try to access the dictionary the structs values property is never updated.
var collection = new ItemCollection { new Item() }; // pre-loaded with an item
collection[0].Values.Add("myKey", "myValue");
Trace.WriteLine(collection[0].Values["myKey"]); // KeyNotFoundException here
However if I load up the item first and then add it to a collection the values field is maintained.
var collection = new ItemCollection();
var item = new Item();
item.Values.Add("myKey", "myValue");
collection.Add(item);
Trace.WriteLine(collection[0].Values["myKey"]); // ok
I've already decided that a struct is the wrong option for this type, and when using a class the issue doesn't occur, but I'm curious what's different between the two methods. Can anybody explain what's happening?
