Accessing grouped settings in a config file but NOT the app.config
public class CustomFieldElement : ConfigurationElement
{
    [ConfigurationProperty("fieldName", DefaultValue = "", IsKey = true, IsRequired = true)]
    public string fieldName
    {
        get { return (string)base["fieldName"]; }
        set { base["fieldName"] = value; }
    }
    [ConfigurationProperty("fieldType", DefaultValue = "", IsKey = true, IsRequired = true)]
    public string fieldType
    {
        get { return (string)base["fieldType"]; }
        set { base["fieldType"] = value; }
    }

    [ConfigurationProperty("xpath", DefaultValue = "", IsKey = true, IsRequired = true)]
    public string xpath
    {
        get { return (string)base["xpath"]; }
        set { base["xpath"] = value; }
    }
}

[ConfigurationCollection(typeof(CustomFieldElement))]
public class FieldAppearanceCollection : ConfigurationElementCollection
{
    internal const string PropertyName = "FieldDescription";

    public override ConfigurationElementCollectionType CollectionType
    {
        get
        {
            return ConfigurationElementCollectionType.BasicMapAlternate;
        }
    }
    protected override string ElementName
    {
        get
        {
            return PropertyName;
        }
    }

    protected override bool IsElementName(string elementName)
    {
        return elementName.Equals(PropertyName, StringComparison.InvariantCultureIgnoreCase);
    }


    public override bool IsReadOnly()
    {
        return false;
    }


    protected override ConfigurationElement CreateNewElement()
    {
        return new CustomFieldElement();
    }

    protected override object GetElementKey(ConfigurationElement element)
    {
        return ((CustomFieldElement)(element)).fieldName;
    }

    public CustomFieldElement this[int idx]
    {
        get
        {
            return (CustomFieldElement)BaseGet(idx);
        }
    }
}

public class ConnectionSection : ConfigurationSection
{
    [ConfigurationProperty("fields")]
    public FieldAppearanceCollection FieldElement
    {
        get { return ((FieldAppearanceCollection)(base["fields"])); }
        set { base["fields"] = value; }
    }
}

public class ConfigSettings
{
    public ConnectionSection CustomFieldAppearanceConfiguration
    {
        get
        {
            return (ConnectionSection)ConfigurationManager.GetSection("customFields");
        }
    }

    public FieldAppearanceCollection CustomFieldApperances
    {
        get
        {
            return this.CustomFieldAppearanceConfiguration.FieldElement;
        }
    }

    public IEnumerable<CustomFieldElement> CustomFieldElements
    {
        get
        {
            foreach (CustomFieldElement selement in this.CustomFieldApperances)
            {
                if (selement != null)
                    yield return selement;
            }
        }
    }
}