Using SQL Server Metadata and Statistics to Build a Table Explorer Application

using System;
using System.Collections.Generic;
using System.Text;
using System.Xml;

/*
	Class to represent the central configuration document
	Exposes the Xml docs, defines the tags to be used and 
	creates nodes etc.
	
	Use singleto pattern and have a static instance object 
	
*/

namespace DbView
{

	class ConfigDoc : XmlDocument
	{
		public const String CFGELM_DOC = "DBVIEW_CONFIG";

		public const String CFGELM_CONNECTIONS = "Connections";
		public const String CFGELM_CONNECTION = "Connection";
		public const String CFGELM_FAVOURITES = "Favourites";
		public const String CFGELM_FAVOURITE = "Favourite";
		public const String CFGELM_VIEWLINKS = "Links";
		public const String CFGELM_VIEWLINK = "Link";
		public const String CFGELM_VIEWDEFS = "Views";
		public const String CFGELM_VIEWDEF = "View";
	
		// view defs
		public const String CFGVIEWDEF_VIEWCOL = "ViewCol";
		public const String CFGVIEWDEF_SORTCOL = "SortCol";
		public const String CFGVIEWDEF_FILTERCOL = "FilterCol";
		public const String CFGVIEWDEF_NUMFILTERCOL = "NumFilterCol";
		public const String CFGVIEWDEF_EXTRAINFO = "Extra";
		public const String CFGVIEWDEF_FILTER = "Filter";
		public const String CFGVIEWDEF_JOINCLAUSE = "Join";
		
	
		public const String CFGATT_CONN = "conn";
		public const String CFGATT_NAME = "name";
		public const String CFGATT_DBOBJNAME = "name";
		public const String CFGATT_DBOBJTTYPE = "objtype";
		public const String CFGATT_TABLE = "table";
		public const String CFGATT_SERVER = "srvr";
		public const String CFGATT_DATABASE = "db";
		public const String CFGATT_USER = "uid";
		public const String CFGATT_PASSWORD = "pwd";
	
		public static ConfigDoc Instance
		{
			get 
			{
				if (theConfig == null)
					theConfig = new ConfigDoc();
				return theConfig;
			}
		}
	
		// careful with name Load() is used by the base class
		public void LoadConfig(String fileName)
		{
			try 
			{
				this.Load(fileName);
			}
			catch (System.IO.FileNotFoundException exc)
			{
				// Add root element
				XmlNode node = this.CreateElement(CFGELM_DOC);
				this.AppendChild(node);
			}
		}
	
		// careful with name Save() is used by the base class
		public void SaveConfig(String fileName)
		{
			this.Save(fileName);
		}
		
		// note send in the group name: appends a new element with the correct name
		public XmlNode CreateNewRecordInGroup(String GroupElementName)
		{
			String newElementName = (GroupElementName == CFGELM_FAVOURITES) ? CFGELM_FAVOURITE :
									(GroupElementName == CFGELM_VIEWLINKS) ? CFGELM_VIEWLINK :
									(GroupElementName == CFGELM_VIEWDEFS) ? CFGELM_VIEWDEF :
									(GroupElementName == CFGELM_CONNECTIONS) ? CFGELM_CONNECTION : "";
			if (newElementName.Length == 0)
				throw new Exception(String.Format("{0} not a config group element name",GroupElementName)); 

			XmlNode node = this.CreateElement(newElementName);
			XmlNode groupNode = getGroupNode(GroupElementName);
			groupNode.AppendChild(node);
			return node;
		}

		public XmlNode CreateNewChild(XmlNode parent, String ChildElementName)
		{
			XmlNode node = this.CreateElement(ChildElementName);
			parent.AppendChild(node);
			return node;
		}

		public void RemoveRecord(XmlNode node)
		{
			XmlNode parent = node.ParentNode;
			if (parent != null)
				parent.RemoveChild(node);
		}

		public XmlNode Connections
		{
			get { return getGroupNode(CFGELM_CONNECTIONS); }
		}

		public XmlNode Views
		{
			get { return getGroupNode(CFGELM_VIEWDEFS); }
		}

		public XmlNode Viewlinks
		{
			get { return getGroupNode(CFGELM_VIEWLINKS); }
		}

		public XmlNode Favourites
		{
			get { return getGroupNode(CFGELM_FAVOURITES); }
		}

		XmlNode getGroupNode(String GroupElementName)
		{
			String xpath = String.Format("/{0}/{1}", CFGELM_DOC, GroupElementName);
			XmlNode node = this.SelectSingleNode(xpath);
			if (node == null)
			{
				node = this.CreateElement(GroupElementName);
				this.DocumentElement.AppendChild(node);
			}
			return node;
		}
		
		public void AddAttribute(XmlNode node, String attName, String attVal)
		{
			XmlAttribute att = this.CreateAttribute(attName);
			node.Attributes.Append(att);
			att.Value = attVal;
		}
	
		public String AttributeValue(XmlNode node, String attName, String defaultVal)
		{
			XmlAttribute att = node.Attributes[attName];
			if (att == null) return defaultVal;
			return att.Value;
		}
		
		public String AttributeValue(XmlNode node, String attName)
		{
			return AttributeValue(node, attName, "");
		}
	
		public String ElementText(XmlNode node, String elementName)
		{
			XmlNode tgtNode = node.SelectSingleNode(elementName);
			if (tgtNode == null) return "";
			return tgtNode.InnerText;
		}

		public List<String> Elements(XmlNode node, String elementName)
		{	
			List<String> data = new List<string>();
			XmlNodeList Nodes = node.SelectNodes(elementName);
			foreach (XmlNode n in Nodes)
				data.Add(n.InnerText);
			return data;
		}
	
		static ConfigDoc theConfig = null;
	}
}