using System;
using System.Xml;
using System.Xml.XPath;
using System.Xml.Serialization;
using System.Configuration;

namespace ConfigSectionHandler
{
	/// <summary>
	/// This class contains only one method, Create().
	/// This is designed to handle custom sections in an Applications Configuration file.
	/// By Implementing <see cref="IConfigurationSectionHandler"/>, we can implement the
	/// Create method, which will provide the XmlNode from the configuration file. This is
	/// Deserialized into an object and passed back to the Caller.
	/// </summary>
	/// <example>
	/// Here is a configuration file entry in the <c>configSections</c> sectikon of the <c>App.Config</c>
	/// file.
	///<code>	///
	///&lt;section name="ServerConfig" type="ConfigSectionHandler.ConfigSectionHandler, ConfigSectionHandler" /&gt;
	///</code>
	///This tells the CLR that there is a section further in, with a node name of <c>ServerConfig</c>. When this section
	///is to be parsed, an object of type <c>ConfigSectionHandler.ConfigSectionHandler</c> which resides in the 
	///assembly <c>ConfigSectionHandler</c> will be instantiated. The CLR automatically calls a method in that object
	///called <c>Create</c>
	///</example>
	public class ConfigSectionHandler : IConfigurationSectionHandler
	{
		public ConfigSectionHandler() : base()
		{
		}
	
		#region IConfigurationSectionHandler Members

		/// <summary>
		/// A method which is called by the CLR when parsing the App.Config file. If custom sections
		/// are found, then an entry in the configuration file will tell the runtime to call this method,
		/// passing in the XmlNode required.
		/// </summary>
		/// <param name="parent">The configuration settings in a corresponding parent configuration section. Passed in via the CLR</param>
		/// <param name="configContext">An <see cref="HttpConfigurationContext"/> when Create is called from the ASP.NET configuration system. Otherwise, 
		/// this parameter is reserved and is a null reference (Nothing in Visual Basic). Passed in via the CLR</param>
		/// <param name="section">The <see cref="XmlNode"/> that contains the configuration information from the configuration file. 
		/// Provides direct access to the XML contents of the configuration section. 	Passed in via the CLR.</param>
		/// <returns>The Deserialized object as an object</returns>
		/// <exception cref="System.Configuration.ConfigurationException">The Configuration file is not well formed,
		/// or the Custom section is not configured correctly, or the type of configuration handler was not specified correctly
		/// or the type of object was not specified correctly.
		/// or the copn</exception>
		public object Create(object parent, object configContext, System.Xml.XmlNode section)
		{
			XPathNavigator xNav=section.CreateNavigator();
			string typeOfObject=(string) xNav.Evaluate("string(@type)");
			Type t=Type.GetType(typeOfObject);
			XmlSerializer ser=new XmlSerializer(t);
			XmlNodeReader xNodeReader=new XmlNodeReader(section);
			return ser.Deserialize(xNodeReader);
		}
		#endregion
	}
}