Using the Properties.Settings file

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I am trying to store a collection of custom types in a Properties.Settings
file which I will be updating at run time and saving on exit of the program.
I understand how to use the Properties.Settings file in this way for normal
types (ints, chars etc) but I am struggling to get it to work for my own
types.

The type I want to use in the Settings file is a custom implementation of
the generic Dictionary class using a string and another custom type (so -
MyCustomType : Dictionary<string, MyOtherCustomType>). The MyOtherCustomType
class is also a custom implementation of a generic container, it is a List of
MyObject's (so - MyOtherCustomType : List<MyObject>). And finally the
MyObject class stores an enum and a Color.

Now, I have already got the Properties.System file to work for the
MyOtherCustomType class but I can't seem to get it to work for the
MyCustomType class. I understand that I need to implement IXmlSerializable
but I am unsure of whether it should be implemented in the MyCustomType class
only or whether all my own types / objects that I want to be serialized with
the class need to implement it too. I am also unsure about how to implement
the interface's ReadXml and WriteXml methods. I have read a post on this
forum in answer to a similar question and tried to adapt their code to suit
my own but had no luck. Can anyone give me a brief outline of what these
methods should do relative to my types / objects?

Thanks,

James