Cannot cast from KeyValueConfigurationCollection to derived class

Question

Trying to handle (internally) KeyValueConfigurationCollection exceptions when a value from it indexer doesn't exists, I have an error.

public class ConfigCore
{

    public static Configuration config 
    {
        get 
        {
             ExeConfigurationFileMap configFileMap = new ExeConfigurationFileMap();
             configFileMap.ExeConfigFilename = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), "App.config");
             return ConfigurationManager.OpenMappedExeConfiguration(configFileMap, ConfigurationUserLevel.None);
        }
    }

    public static SettingsManager Settings
    {
        get
        {
            //config is an instance of System.Configuration.Configuration and works well.
            return (SettingsManager) config.AppSettings.Settings;
        }
    }

    internal static KeyValueConfigurationCollection Setts
    {
        get
        {
            return config.AppSettings.Settings;
        }
    }

    public static void CreateSettingEntry(string key, string value)
    {
        try
        {
            Setts.Add(key, value);
        }
        catch (Exception ex)
        {
            Console.WriteLine("Error ocurred trying to add value to Config. Message: {0}", ex.ToString());
        }
    }
}

public class SettingsManager : KeyValueConfigurationCollection
{
    public KeyValueConfigurationElement this[string key]
    {
        get
        {
            if (ConfigCore.Setts[key] == null)
                ConfigCore.CreateSettingEntry(key, "");
            return ConfigCore.Setts[key];
        }
    }
}

I want to avoid that a user does the following thing using my API:

if(ConfigCore.Settings["key"] == null)
    ConfigCore.CreateSettingEntry("key", "");

ConfigCore.Settings["key"].Value = "value";

And by this reason I have created an internal indexer to search for this cases and call automatically the method that creates the entry before setting it.

But for some reason, an exception occurs saying that KeyValueConfigurationCollection cannot be casted into SettingsManager, why if SettingsManager is a inherited class of KeyValueConfigurationCollection, what I'm forgetting?

Thanks in advance!

Answer 1

I have been working on this issue just today.

public static class KeyValueConfigurationCollectionExtension 
    {
        public static bool ContainsKey<T>(T key)
        {
            System.Collections.Specialized.NameValueCollection coll = new System.Collections.Specialized.NameValueCollection();

            string keyValue = key.ToString();
            int upperBound = coll.Count;
            List<string> items = new List<string>();
            for(int i = 0; i < upperBound; i++)
            {
                items.Add(coll[i].ToString());
            }

            int index = items.IndexOf(keyValue);
            if(index >= 0)
                return true;

            return false;

        }
    }