Saving an ArrayList of custom objects to user settings

Question

Is it possible to save an ArrayList of custom objects to the application user settings without resorting to custom serialization?

For example, given a basic data class containing only public get/set properties and private backing fields:

[Serializable]
class SimpleClass()
{
  ...   
}

When I run the following in code, and then restart the application, the ArrayList setting named MyList is always null, ie it was not saved.

if (Properties.Settings.Default.MyList==null)
{
    Properties.Settings.Default.MyList=new ArrayList();
}

Properties.Settings.Default.MyList.Add(new SimpleClass(DateTime.Now.ToString()));

Properties.Settings.Default.Save();

I realise that an ArrayList is not typed, ie. it holds a collection of objects. However it is simple to use GetType() on each object to determine the actual type. This should allow serialization to occur, shouldn't it?

I also know how to get around this performing some custom serialization. It's just a pain this doesn't appear to work as it would be by far the most convenient for simpler situations.

Any ideas?

Answer 1

If you are using XML Serialization, you can use the XmlArrayItem attribute.

 [XmlArray("Items")]
 [XmlArrayItem("A.Thing",typeof(Thing))]
 [XmlArrayItem("A.Different.Thing",typeof(Whatzit))]
 public System.Collections.ArrayList List;

This requires that you know the different types that may be present in the ArrayList at compile time.