Custom config section with recursive ConfigurationElement

Question

I am trying to create a custom configuration section that represents the following xml structure:

<observerSettings>
   <jobSettings>
      <filter key="location" value="de">
        <filter key="type" value="MyType1">
          <filter key="status" value="failed">
            <actions>
              <notify timespan="12.00:00:00">
                <mailSettings>
                  <mailAddress to="mail1@something.com" />
                  <mailAddress to="mail2@something.com" />
                </mailSettings>
              </notify>
              <remove timespan="14.00:00:00">
                <mailSettings>
                  <mailAddress to="mail1@something.com" />
                  <mailAddress to="mail2@something.com" />
                </mailSettings>
              </remove>
            </actions> 
          </filter>
        </filter>
      </filter>
   </jobSettings>
</observerSettings>

The FilterConfigElement is defined like this:

internal class FilterConfigElement : ConfigurationElement, IFilterConfigElement
{
        [ConfigurationProperty("filter", IsRequired = false)]
        public FilterConfigElement ChildFilter => base["filter"] as FilterConfigElement;

        [ConfigurationProperty("actions", IsRequired = false)]
        public ActionsConfigElement Actions => base["actions"] as ActionsConfigElement;

        [ConfigurationProperty("key", IsRequired = true)]
        public string Key => base["key"] as string;

        [ConfigurationProperty("value", IsRequired = false)]
        public string Value => base["value"] as string;
}

When accessing the config section like below, the application is crashing with a StackOverflow exception:

internal class ObserverSettings : ConfigurationSection, IObserverSettings
{
   public static IObserverSettings Instance { get; private set; } = ConfigurationManager.GetSection("observerSettings") as ObserverSettings;

   [ConfigurationProperty("jobSettings")]
   protected JobSettingsCollection JobSettingsCollection => base["jobSettings"] as JobSettingsCollection;

   public virtual IJobSettingsCollection JobSettings => JobSettingsCollection;
}

So I assume ConfigurationManager is creating this structure with infinite depth and not stopping when the last filter element is reached. Can this be limited somehow? Is such structure even supported?

Matthias · Answer 1 · 2019-09-18T08:49:55.863

Ok, after digging through the implementation of ConfigurationElement it seems to be not possible at all to create recursive structures the way I tried.

Cause of the problem is the implementation of PropertiesFromType where assignment of the properties to s_propertyBags is done after the call to CreatePropertyBagFromType and thus creating an endless recursion where properties is always null.

private static bool PropertiesFromType(Type type, out ConfigurationPropertyCollection result)
{
   ConfigurationPropertyCollection properties = (ConfigurationPropertyCollection)s_propertyBags[type];
   result = null;
   bool firstTimeInit = false;
   if (properties == null) /*code omitted*/
   {
      properties = CreatePropertyBagFromType(type);
      s_propertyBags[type] = properties;
      firstTimeInit = true;
   }
   result = properties;
   return firstTimeInit;
}

Source: https://referencesource.microsoft.com/#System.Configuration/System/Configuration/ConfigurationElement.cs

Edit:

Only workaround to keep some kind of "recursive" structure was to wrap all child FilterConfigElements into a ConfigurationElementCollection with element name childFilter. This leads to following not so nice but acceptable config structure:

<jobSettings>
  <filter key="location" value="de">
    <childFilter>
      <filter key="type" value="MyType1">
        <childFilter>
          <filter key="status" value="failed">
            <actions>
              <!-- ... -->
            </actions>
          </filter>
        </childFilter>
      </filter>
    </childFilter>
  </filter>
</jobSettings>

Source: Recursive Custom Configuration in c#

Custom config section with recursive ConfigurationElement

1 Answers1