ConfigSectionHandler for Hierarchical configs

Here is a quick way to create a ConfigSection Handler for reading Hierarchical configs. For e.g. suppose you need to read a config file which has the following structure:

MySpace
 
  23
   Rohit
  Gupta
  

For this you would create the 2 classes, one for the Parent Config and another for the chold config like this:

  [XmlRoot("MainConfig")]
   public class MainConfig
   {
       private static readonly MainConfig instance =
 (MainConfig)ConfigurationManager.GetSection("MainConfig");
       public static MainConfig GetInstance()
       {
           if (instance == null)
               throw new ConfigurationErrorsException(
                   "Unable to locate or deserialize the 'MainConfig' section.");

           return instance;
       }

       public string Company { get; set; }

       public SubConfig FriendsConfig { get; set; }
   }

   [XmlRoot("SubConfig")]
   public class SubConfig
   {
       public int ID { get; set; }
       public string Name { get; set; }
       public string LastName { get; set; }
   }

Then you would create a configsectionHandler class which reads the config from the .config file:

public class MainConfigSectionHandler : IConfigurationSectionHandler
   {
       #region IConfigurationSectionHandler Members

       public object Create(object parent, object configContext, System.Xml.XmlNode section)
       {
           MainConfig typedConfig = GetConfig(section);

           if (typedConfig != null)
           {
               #region Get Sub Configs
               foreach (XmlNode node in section.ChildNodes)
               {
                   switch (node.Name)
                   {
                       case "SubConfig":
                           SubConfig friendsConfig = GetConfig(node);
                           typedConfig.FriendsConfig = friendsConfig;
                           break;
                       default:
                           break;
                   }
               }
               #endregion
           }


           return typedConfig;
       }

       public T GetConfig(System.Xml.XmlNode section) where T : class
       {
           T sourcedObject = default(T);
           Type t = typeof(T);
           XmlSerializer ser = new XmlSerializer(typeof(T));
           sourcedObject = ser.Deserialize(new XmlNodeReader(section)) as T;
           return sourcedObject;
       }

       #endregion

   }

After this you would add a entry in the app.config for this configsection Handler as the following:

Finally to read this config, you would write the following:

MainConfig config = MainConfig.GetInstance(); Console.WriteLine(config.Company);
Console.WriteLine(config.FriendsConfig.ID);
Console.WriteLine(config.FriendsConfig.LastName);
Console.WriteLine(config.FriendsConfig.Name);

Lucene: Multifield searches

We can run multifield searches in Lucene using either the BooleanQuery API or using the MultiFieldQueryParser for parsing the query text. For e.g. If a index has 2 fields FirstName and LastName and if you need to search for "John" in the FirstName field and "Travis" in the LastName field one can use a Boolean Query as such:

BooleanQuery bq = new BooleanQuery();
Query qf = new TermQuery(new Lucene.Net.Index.Term("FirstName", "John"));
Query ql = new TermQuery(new Lucene.Net.Index.Term("LastName", "Travis"));
bq.Add(qf, BooleanClause.Occur.MUST);
bq.Add(ql, BooleanClause.Occur.MUST);
IndexSearcher srchr = new IndexSearcher(@"C:\indexDir");
srchr.Search(bq);

Now if we need to search a single term across either of the FirstName and LastName fields then we can use the MultiFieldQueryParser as follows:

Query query = MultiFieldQueryParser.parse("commonName",
new String[] { "FirstName", "LastName" },
new SimpleAnalyzer());
srchr.Search(query);

Now if you need to search the term that must exist in both the fields then we use the following:

 Query query = MultiFieldQueryParser.Parse("commonName",
new String[] { "FirstName", "LastName" },
new BooleanClause.Occur[] { BooleanClause.Occur.MUST,BooleanClause.Occur.MUST}
, new SimpleAnalyzer());
srchr.Search(query);

Finally if you don’t want a term to occur in one of the Fields (say FirstName) then use:

 Query query = MultiFieldQueryParser.Parse("commonName",
new String[] { "FirstName", "LastName" },
new BooleanClause.Occur[] { BooleanClause.Occur.MUST_NOT,BooleanClause.Occur.MUST},
new SimpleAnalyzer());
srchr.Search(query);  

so if you need to search a single term across multiple fields then use MultiFieldQueryParser, if you need to search different terms in different fields then use the BooleanQuery as shown first