Use something like this:
[ConfigurationProperty("type", IsRequired = true)]
[TypeConverter(typeof(TypeNameConverter)), SubclassTypeValidator(typeof(MyBaseType))]
public Type ValueType
{
get
{
return (Type)this["type"];
}
set
{
this["type"] = value;
}
}
The use of SubclassTypeValidator is not absolutely necessary, but most of the times you would use it ... I do at least.