Неизвестный элементный процессор — раздел «Пользовательская конфигурация»

Пытаюсь добавить пользовательский раздел конфигурации после другого поста здесь, но получаю сообщение об ошибке:

Произошло необработанное исключение типа «System.Configuration.ConfigurationErrorsException» в System.Configuration.dll.

Дополнительная информация: Нераспознанный элемент «Процессор».

в этой строке:

return (ProcessorsConfig)ConfigurationManager.GetSection("Processors") ?? new ProcessorsConfig();

вот мой код:

public class ProcessorsConfig : ConfigurationSection
{
    public static ProcessorsConfig GetConfig()
    {
        return (ProcessorsConfig)ConfigurationManager.GetSection("Processors") ?? new ProcessorsConfig();
    }

    [ConfigurationProperty("Processors")]
    [ConfigurationCollection(typeof(Processors), AddItemName = "Processor")]
    public Processors Processors
    {
        get
        {
            object o = this["Processors"];
            return o as Processors;
        }
    }
}



[ConfigurationCollection(typeof(Processor), AddItemName="Processor", CollectionType = ConfigurationElementCollectionType.BasicMap)]
public class Processors : ConfigurationElementCollection
{
    public Processor this[int index]
    {
        get
        {
            return base.BaseGet(index) as Processor;
        }
        set
        {
            if (base.BaseGet(index) != null)
                base.BaseRemoveAt(index);

            this.BaseAdd(index, value);
        }
    }

    public new Processor this[string responseString]
    {
        get { return (Processor)BaseGet(responseString); }
        set
        {
            if (BaseGet(responseString)!=null)
                BaseRemoveAt(BaseIndexOf(BaseGet(responseString)));

            BaseAdd(value);
        }
    }

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

    protected override object GetElementKey(ConfigurationElement element)
    {
        return ((Processor)element).Name;
    }
}

public class Processor : ConfigurationElement
{
    [ConfigurationProperty("name", IsRequired=true)]
    public string Name
    {
        get
        {
            return this["name"] as string;
        }           
    }

    [ConfigurationProperty("searchPattern", IsRequired = true)]
    public string SearchPattern
    {
        get
        {
            return this["searchPattern"] as string;
        }
    }

    [ConfigurationProperty("collectionFolder", IsRequired = true)]
    public string CollectionFolder
    {
        get
        {
            return this["collectionFolder"] as string;
        }
    }

    [ConfigurationProperty("failureFolder", IsRequired = true)]
    public string FailureFolder
    {
        get
        {
            return this["failureFolder"] as string;
        }
    }

    [ConfigurationProperty("xmlOutputFolder", IsRequired = true)]
    public string XMLOutputFolder
    {
        get
        {
            return this["xmlOutputFolder"] as string;
        }
    }
}

и мой app.config:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="Processors" type="Ideagen.PHE_PMEP_Processor_v2.Config.ProcessorsConfig, PHEPMEPProcessorv2"/>
  </configSections>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.1" />
  </startup>
  <appSettings>
  </appSettings>

  <Processors>
    <Processor name="test" collectionFolder="c:\temp\phev2\collection" searchPattern="*.txt" failureFolder="c:\temp\phev2\failure" xmlOutputFolder="c:\temp\phev2\xmlout"></Processor>
  </Processors>
</configuration>

Любые подсказки?