Nested custom elements in app.config (C#)

G'da to everyone,

For hours I've been trying to figure how to read settings from app.config file:

The the code for custom handler classes is here, also copied below:

public class DatabaseSection : ConfigurationSection
{
    [ConfigurationProperty("Databases", IsDefaultCollection = false)]
    public DatabaseInstanceCollection Databases
    {
        get { return (DatabaseInstanceCollection)this["Databases"]; }
        set { this[""] = value; }
    }
}
[ConfigurationCollection(typeof(DatabaseElement), AddItemName = "add", CollectionType = ConfigurationElementCollectionType.BasicMap )]
public class DatabaseInstanceCollection : ConfigurationElementCollection
{
    protected override ConfigurationElement CreateNewElement()
    {
        return new DatabaseElement();
    }
    protected override object GetElementKey(ConfigurationElement element)
    {
        return ((DatabaseElement)element).Name;
    }
}
public class DatabaseElement : ConfigurationElement
{
    [ConfigurationProperty("name", IsKey = true, IsRequired = true)]
    public string Name
    {
        get { return (string)base["name"]; }
        set { base["name"] = value; }
    }
}

public class TableSection : ConfigurationSection
{
    [ConfigurationProperty("Tables", IsDefaultCollection = true)]
    public TableInstanceCollection Tables
    {
        get { return (TableInstanceCollection)this["Tables"]; }
        set { this[""] = value; }
    }
}

[ConfigurationCollection(typeof(TableElement), AddItemName = "Table", CollectionType = ConfigurationElementCollectionType.BasicMap)]
public class TableInstanceCollection : ConfigurationElementCollection
{
    protected override ConfigurationElement CreateNewElement()
    {
        return new TableElement();
    }
    protected override object GetElementKey(ConfigurationElement element)
    {
        return ((TableElement)element).Name;
    }
}

public class TableElement : ConfigurationElement
{
    [ConfigurationProperty("name", IsKey = true, IsRequired = true)]
    public string Name
    {
        get { return (string)base["name"]; }
        set { base["name"] = value; }
    }
}

public class ColumnSection : ConfigurationSection
{
    [ConfigurationProperty("Columns", IsDefaultCollection = true)]
    public ColumnInstanceCollection Columns
    {
        get { return (ColumnInstanceCollection)this["Columns"]; }
        set { this[""] = value; }
    }
}

[ConfigurationCollection(typeof(ColumnElement), AddItemName = "Column", CollectionType = ConfigurationElementCollectionType.BasicMap)]
public class ColumnInstanceCollection : ConfigurationElementCollection
{
    protected override ConfigurationElement CreateNewElement()
    {
        return new ColumnElement();
    }
    protected override object GetElementKey(ConfigurationElement element)
    {
        return ((ColumnElement)element).Name;
    }
}

public class ColumnElement : ConfigurationElement
{
    [ConfigurationProperty("name", IsKey = true, IsRequired = true)]
    public string Name
    {
        get { return (string)base["name"]; }
        set { base["name"] = value; }
    }
}

The problem is when I attempt to get "Databases" section via GetSection method:

Configuration Config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
DatabaseSection DbConfig = Config.GetSection("Databases") as DatabaseSection;

program throws an ConfigurationErrorsException, reporting "Unrecognized element 'Database'", although it does that after going through get method of DatabaseSection, even though I define AddItemName for DatabaseInstanceCollection as "Database". Am I missing something, attribute that will let underlying code read the app.config correctly?