/// <summary>
		/// Gets a free element ID from the database.
		/// </summary>
		/// <param name="element">The element type.</param>
		/// <param name="transaction">The current database transaction.</param>
		/// <returns>The free element ID.</returns>
		private uint GetFreeElementId(IndexElementType element, DbTransaction transaction) {
			if(element == IndexElementType.Occurrences) throw new ArgumentException("Element cannot be Occurrences", "element");

			string table = element == IndexElementType.Documents ? "IndexDocument" : "IndexWord";

			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom(table, new string[] { "Id" });
			query = queryBuilder.OrderBy(query, new string[] { "Id" }, new Ordering[] { Ordering.Desc });

			DbCommand command = builder.GetCommand(transaction, query, new List<Parameter>());

			int id = ExecuteScalar<int>(command, -1, false);

			if(id == -1) return 0;
			else return (uint)id + 1;
		}
		/// <summary>
		/// Gets all the sub-namespaces.
		/// </summary>
		/// <returns>The sub-namespaces, sorted by name.</returns>
		public NamespaceInfo[] GetNamespaces() {
			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			// select ... from Namespace left join Page on Namespace.DefaultPage = Page.Name where Namespace.Name <> '' and (Namespace.DefaultPage is null or Page.Namespace <> '')
			string query = queryBuilder.SelectFrom("Namespace", "Page", "DefaultPage", "Name", Join.LeftJoin, new string[] { "Name", "DefaultPage" }, new string[] { "CreationDateTime" });
			query = queryBuilder.Where(query, "Namespace", "Name", WhereOperator.NotEquals, "Empty1");
			query = queryBuilder.AndWhere(query, "Namespace", "DefaultPage", WhereOperator.IsNull, null, true, false);
			query = queryBuilder.OrWhere(query, "Page", "Namespace", WhereOperator.NotEquals, "Empty2", false, true);
			query = queryBuilder.OrderBy(query, new[] { "Namespace_Name" }, new[] { Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(2);
			parameters.Add(new Parameter(ParameterType.String, "Empty1", " "));
			parameters.Add(new Parameter(ParameterType.String, "Empty2", " "));

			DbCommand command = builder.GetCommand(connString, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<NamespaceInfo> result = new List<NamespaceInfo>(10);

				while(reader.Read()) {
					string realName = reader["Namespace_Name"] as string;
					string page = GetNullableColumn<string>(reader, "Namespace_DefaultPage", null);
					PageInfo defaultPage = string.IsNullOrEmpty(page) ? null :
						new PageInfo(NameTools.GetFullName(realName, page), this, (DateTime)reader["Page_CreationDateTime"]);

					// The query returns duplicate entries if the main page of two or more namespaces have the same name
					if(result.Find(n => { return n.Name.Equals(realName); }) == null) {
						result.Add(new NamespaceInfo(realName, this, defaultPage));
					}
				}

				CloseReader(command, reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Adds a new Message to a Page.
		/// </summary>
		/// <param name="page">The Page.</param>
		/// <param name="username">The Username.</param>
		/// <param name="subject">The Subject.</param>
		/// <param name="dateTime">The Date/Time.</param>
		/// <param name="body">The Body.</param>
		/// <param name="parent">The Parent Message ID, or -1.</param>
		/// <returns>True if the Message is added successfully.</returns>
		/// <exception cref="ArgumentNullException">If <paramref name="page"/>, <paramref name="username"/>, <paramref name="subject"/> or <paramref name="body"/> are <c>null</c>.</exception>
		/// <exception cref="ArgumentException">If <paramref name="username"/> or <paramref name="subject"/> are empty.</exception>
		/// <exception cref="ArgumentOutOfRangeException">If <paramref name="parent"/> is less than -1.</exception>
		public bool AddMessage(PageInfo page, string username, string subject, DateTime dateTime, string body, int parent) {
			if(page == null) throw new ArgumentNullException("page");
			if(username == null) throw new ArgumentNullException("username");
			if(username.Length == 0) throw new ArgumentException("Username cannot be empty", "username");
			if(subject == null) throw new ArgumentNullException("subject");
			if(subject.Length == 0) throw new ArgumentException("Subject cannot be empty", "subject");
			if(body == null) throw new ArgumentNullException("body"); // body can be empty
			if(parent < -1) throw new ArgumentOutOfRangeException("parent", "Invalid Parent Message ID");

			string nspace, name;
			NameTools.ExpandFullName(page.FullName, out nspace, out name);
			if( string.IsNullOrEmpty(nspace)||string.IsNullOrEmpty(nspace.Trim())) nspace = " ";

			ICommandBuilder builder = GetCommandBuilder();
			DbConnection connection = builder.GetConnection(connString);
			DbTransaction transaction = BeginTransaction(connection);

			if(parent != -1 && FindMessage(GetMessages(transaction, page), parent) == null) {
				RollbackTransaction(transaction);
				return false;
			}

			QueryBuilder queryBuilder = new QueryBuilder(builder);

			short freeId = -1;

			string query = queryBuilder.SelectFrom("Message", new string[] { "Id" });
			query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");
			query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");
			query = queryBuilder.OrderBy(query, new string[] { "Id" }, new Ordering[] { Ordering.Desc });

			List<Parameter> parameters = new List<Parameter>(2);
			parameters.Add(new Parameter(ParameterType.String, "Page", name));
			parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));

			DbCommand command = builder.GetCommand(transaction, query, parameters);

			freeId = ExecuteScalar<short>(command, -1, false);

			if(freeId == -1) freeId = 0;
			else freeId++;

			query = queryBuilder.InsertInto("Message", new string[] { "Page", "Namespace", "Id", "Parent", "Username", "Subject", "DateTime", "Body" },
				new string[] { "Page", "Namespace", "Id", "Parent", "Username", "Subject", "DateTime", "Body" });

			parameters = new List<Parameter>(8);
			parameters.Add(new Parameter(ParameterType.String, "Page", name));
			parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));
			parameters.Add(new Parameter(ParameterType.Int16, "Id", freeId));
			if(parent != -1) parameters.Add(new Parameter(ParameterType.Int16, "Parent", parent));
			else parameters.Add(new Parameter(ParameterType.Int16, "Parent", DBNull.Value));
			parameters.Add(new Parameter(ParameterType.String, "Username", username));
			parameters.Add(new Parameter(ParameterType.String, "Subject", subject));
			parameters.Add(new Parameter(ParameterType.DateTime, "DateTime", dateTime));
			parameters.Add(new Parameter(ParameterType.String, "Body", body));

			command = builder.GetCommand(transaction, query, parameters);

			int rows = ExecuteNonQuery(command, false);

			if(rows == 1) {
				IndexMessage(page, freeId, subject, dateTime, body, transaction);

				CommitTransaction(transaction);
				return true;
			}
			else {
				RollbackTransaction(transaction);
				return false;
			}
		}
		/// <summary>
		/// Gets all the Navigation Paths in a Namespace.
		/// </summary>
		/// <param name="nspace">The Namespace.</param>
		/// <returns>All the Navigation Paths, sorted by name.</returns>
		public NavigationPath[] GetNavigationPaths(NamespaceInfo nspace) {
			string nspaceName = nspace != null&&!string.IsNullOrEmpty(nspace.Name) ? nspace.Name : " ";

			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("NavigationPath", new string[] { "Name", "Namespace", "Page" });
			query = queryBuilder.Where(query, "Namespace", WhereOperator.Equals, "Namespace");
			query = queryBuilder.OrderBy(query, new string[] { "Namespace", "Name", "Number" }, new Ordering[] { Ordering.Asc, Ordering.Asc, Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(1);
			parameters.Add(new Parameter(ParameterType.String, "Namespace", nspaceName));

			DbCommand command = builder.GetCommand(connString, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<NavigationPath> result = new List<NavigationPath>(10);

				string prevName = "|||";
				string name;
				string actualNamespace = " ";
				List<string> pages = new List<string>(10);

				while(reader.Read()) {
					name = reader["Name"] as string;

					if(name != prevName) {
						actualNamespace = (reader["Namespace"] as string).Trim();
                        actualNamespace = actualNamespace.Trim();

						if(prevName != "|||") {
							result[result.Count - 1].Pages = pages.ToArray();
							pages.Clear();
						}

						result.Add(new NavigationPath(NameTools.GetFullName(actualNamespace, name), this));
					}

					prevName = name;
					pages.Add(NameTools.GetFullName(actualNamespace, reader["Page"] as string));
				}

				if(result.Count > 0) {
					result[result.Count - 1].Pages = pages.ToArray();
				}

				CloseReader(command, reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Gets the users of a group.
		/// </summary>
		/// <param name="connection">A database connection.</param>
		/// <param name="group">The group.</param>
		/// <returns>The users.</returns>
		private string[] GetUserGroupUsers(DbConnection connection, string group) {
			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("UserGroupMembership", new string[] { "User" });
			query = queryBuilder.Where(query, "UserGroup", WhereOperator.Equals, "UserGroup");
			query = queryBuilder.OrderBy(query, new[] { "User" }, new[] { Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(1);
			parameters.Add(new Parameter(ParameterType.String, "UserGroup", group));

			DbCommand command = builder.GetCommand(connection, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<string> result = new List<string>(100);

				while(reader.Read()) {
					result.Add(reader["User"] as string);
				}

				CloseReader(reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Gets the Page Messages.
		/// </summary>
		/// <param name="connection">A database connection.</param>
		/// <param name="page">The Page.</param>
		/// <returns>The list of the <b>first-level</b> Messages, containing the replies properly nested, sorted by date/time.</returns>
		private Message[] GetMessages(DbConnection connection, PageInfo page) {
			if(GetPage(connection, page.FullName) == null) return null;

			// 1. Load all messages in memory in a dictionary id->message
			// 2. Build tree using ParentID

			string nspace, name;
			NameTools.ExpandFullName(page.FullName, out nspace, out name);
			if( string.IsNullOrEmpty(nspace)||string.IsNullOrEmpty(nspace.Trim())) nspace = " ";

			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("Message", new string[] { "Id", "Parent", "Username", "Subject", "DateTime", "Body" });
			query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");
			query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");
			query = queryBuilder.OrderBy(query, new string[] { "DateTime", "Id" }, new Ordering[] { Ordering.Asc, Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(2);
			parameters.Add(new Parameter(ParameterType.String, "Page", name));
			parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));

			DbCommand command = builder.GetCommand(connection, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				Dictionary<short, Message> allMessages = new Dictionary<short, Message>(50);
				List<short> ids = new List<short>(50);
				List<short?> parents = new List<short?>(50);

				while(reader.Read()) {
					Message msg = new Message((short)Convert.ChangeType( reader["Id"],typeof(short)), reader["Username"] as string, reader["Subject"] as string,
						(DateTime)reader["DateTime"], reader["Body"] as string);

					ids.Add((short)msg.ID);

					// Import from V2: parent = -1, otherwise null
					if(!IsDBNull(reader, "Parent")) {
						short par = (short)Convert.ChangeType(reader["Parent"],typeof(short));
						if(par >= 0) parents.Add(par);
						else parents.Add(null);
					}
					else parents.Add(null);

					allMessages.Add((short)msg.ID, msg);
				}

				CloseReader(reader);

				// Add messages to their parents and build the top-level messages list
				List<Message> result = new List<Message>(20);

				for(int i = 0; i < ids.Count; i++) {
					short? currentParent = parents[i];
					short currentId = ids[i];

					if(currentParent.HasValue) {
						List<Message> replies = new List<Message>(allMessages[currentParent.Value].Replies);
						replies.Add(allMessages[currentId]);
						allMessages[currentParent.Value].Replies = replies.ToArray();
					}
					else result.Add(allMessages[currentId]);
				}

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Gets all the categories of a page.
		/// </summary>
		/// <param name="page">The page.</param>
		/// <returns>The categories, sorted by name.</returns>
		/// <exception cref="ArgumentNullException">If <paramref name="page"/> is <c>null</c>.</exception>
		public CategoryInfo[] GetCategoriesForPage(PageInfo page) {
			if(page == null) throw new ArgumentNullException("page");

			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string nspace, pageName;
			NameTools.ExpandFullName(page.FullName, out nspace, out pageName);
			if( string.IsNullOrEmpty(nspace)||string.IsNullOrEmpty(nspace.Trim())) nspace = " ";

			string query = queryBuilder.SelectFrom("Category", "CategoryBinding", new string[] { "Name", "Namespace" }, new string[] { "Category", "Namespace" }, Join.LeftJoin,
				new string[] { "Name", "Namespace" }, new string[] { "Page" });
			query = queryBuilder.Where(query, "CategoryBinding", "Namespace", WhereOperator.Equals, "Namespace");
			query = queryBuilder.AndWhere(query, "CategoryBinding", "Page", WhereOperator.Equals, "Page");
			query = queryBuilder.OrderBy(query, new[] { "Category_Name" }, new[] { Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(2);
			parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));
			parameters.Add(new Parameter(ParameterType.String, "Page", pageName));

			DbCommand command = builder.GetCommand(connString, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<CategoryInfo> result = new List<CategoryInfo>(20);
				List<string> pages = new List<string>(50);

				string prevName = "|||";
				string name = null;

				while(reader.Read()) {
					name = reader["Category_Name"] as string;

					if(name != prevName) {
						if(prevName != "|||") {
							result[result.Count - 1].Pages = pages.ToArray();
							pages.Clear();
						}

						result.Add(new CategoryInfo(NameTools.GetFullName((reader["Category_Namespace"] as string).Trim(), name), this));
					}

					prevName = name;
					if(!IsDBNull(reader, "CategoryBinding_Page")) {
						pages.Add(NameTools.GetFullName((reader["Category_Namespace"] as string).Trim(), reader["CategoryBinding_Page"] as string));
					}
				}

				CloseReader(command, reader);

				if(result.Count > 0) result[result.Count - 1].Pages = pages.ToArray();

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Gets the recent changes of the Wiki.
		/// </summary>
		/// <returns>The recent Changes, oldest to newest.</returns>
		public RecentChange[] GetRecentChanges() {
			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("RecentChange", new string[] { "Page", "Title", "MessageSubject", "DateTime", "User", "Change", "Description" });
			query = queryBuilder.OrderBy(query, new string[] { "DateTime" }, new Ordering[] { Ordering.Asc });

			DbCommand command = builder.GetCommand(connString, query, new List<Parameter>());

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<RecentChange> result = new List<RecentChange>(100);

				while(reader.Read()) {
					result.Add(new RecentChange(reader["Page"] as string, reader["Title"] as string,
						GetNullableColumn<string>(reader, "MessageSubject", " "),
						(DateTime)reader["DateTime"], reader["User"] as string, RecentChangeFromChar(((string)reader["Change"])[0]),
						GetNullableColumn<string>(reader, "Description", "")));
				}

				CloseReader(command, reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Returns the names of the Attachments of a Page.
		/// </summary>
		/// <param name="connection">A database connection.</param>
		/// <param name="pageInfo">The Page Info object that owns the Attachments.</param>
		/// <returns>The names, or an empty list.</returns>
		private string[] ListPageAttachments(DbConnection connection, PageInfo pageInfo) {
			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("Attachment", new string[] { "Name" });
			query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");

			List<Parameter> parameters = new List<Parameter>(1);
			parameters.Add(new Parameter(ParameterType.String, "Page", pageInfo.FullName));
			query = queryBuilder.OrderBy(query, new[] { "Name" }, new[] { Ordering.Asc });

			DbCommand command = builder.GetCommand(connection, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<string> result = new List<string>(10);

				while(reader.Read()) {
					result.Add(reader["Name"] as string);
				}

				CloseReader(reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Gets all the Categories in a namespace.
		/// </summary>
		/// <param name="connection">A database connection.</param>
		/// <param name="nspace">The namespace.</param>
		/// <returns>All the Categories in the namespace. The array is not sorted.</returns>
		private CategoryInfo[] GetCategories(DbConnection connection, NamespaceInfo nspace) {
			string nspaceName = nspace != null&&!string.IsNullOrEmpty(nspace.Name) ? nspace.Name : " ";

			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("Category", "CategoryBinding", new string[] { "Name", "Namespace" }, new string[] { "Category", "Namespace" }, Join.LeftJoin,
				new string[] { "Name", "Namespace" }, new string[] { "Page" });
			query = queryBuilder.Where(query, "Category", "Namespace", WhereOperator.Equals, "Namespace");
			query = queryBuilder.OrderBy(query, new string[] { "Category_Name", "CategoryBinding_Page" }, new Ordering[] { Ordering.Asc, Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(1);
			parameters.Add(new Parameter(ParameterType.String, "Namespace", nspaceName));

			DbCommand command = builder.GetCommand(connection, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<CategoryInfo> result = new List<CategoryInfo>(20);
				List<string> pages = new List<string>(50);

				string prevName = "|||";
				string name = null;

				while(reader.Read()) {
					name = reader["Category_Name"] as string;

					if(name != prevName) {
						if(prevName != "|||") {
							result[result.Count - 1].Pages = pages.ToArray();
							pages.Clear();
						}

						result.Add(new CategoryInfo(NameTools.GetFullName((reader["Category_Namespace"] as string).Trim(), name), this));
					}

					prevName = name;
					if(!IsDBNull(reader, "CategoryBinding_Page")) {
						pages.Add(NameTools.GetFullName((reader["Category_Namespace"] as string).Trim(), reader["CategoryBinding_Page"] as string));
					}
				}

				CloseReader(reader);

				if(result.Count > 0) result[result.Count - 1].Pages = pages.ToArray();

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// The the names of the pages with attachments.
		/// </summary>
		/// <returns>The names of the pages with attachments.</returns>
		public string[] GetPagesWithAttachments() {
			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("Attachment", new string[] { "Page" });
			query = queryBuilder.GroupBy(query, new[] { "Page" });
			query = queryBuilder.OrderBy(query, new[] { "Page" }, new[] { Ordering.Asc });

			DbCommand command = builder.GetCommand(connString, query, new List<Parameter>());

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<string> result = new List<string>(100);

				while(reader.Read()) {
					result.Add(reader["Page"] as string);
				}

				CloseReader(command, reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Lists the Directories in the specified directory.
		/// </summary>
		/// <param name="transaction">A database transaction.</param>
		/// <param name="directory">The full directory name, for example "/my/directory". Null, empty or "/" for the root directory.</param>
		/// <returns>The list of Directories in the Directory.</returns>
		private string[] ListDirectories(DbTransaction transaction, string directory) {
			directory = PrepareDirectory(directory);

			ICommandBuilder builder = GetCommandBuilder();

			if(!DirectoryExists(transaction, directory)) {
				RollbackTransaction(transaction);
				throw new ArgumentException("Directory does not exist", "directory");
			}

			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("Directory", new string[] { "FullPath" });
			query = queryBuilder.Where(query, "Parent", WhereOperator.Equals, "Parent");

			List<Parameter> parameters = new List<Parameter>(1);
			parameters.Add(new Parameter(ParameterType.String, "Parent", directory));
			query = queryBuilder.OrderBy(query, new[] { "FullPath" }, new[] { Ordering.Asc });

			DbCommand command = builder.GetCommand(transaction, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<string> result = new List<string>(20);

				while(reader.Read()) {
					result.Add(reader["FullPath"] as string);
				}

				CloseReader(reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Lists the Files in the specified Directory.
		/// </summary>
		/// <param name="directory">The full directory name, for example "/my/directory". Null, empty or "/" for the root directory.</param>
		/// <returns>The list of Files in the directory.</returns>
		/// <exception cref="ArgumentException">If <paramref name="directory"/> does not exist.</exception>
		public string[] ListFiles(string directory) {
			directory = PrepareDirectory(directory);

			ICommandBuilder builder = GetCommandBuilder();
			DbConnection connection = builder.GetConnection(connString);

			if(!DirectoryExists(connection, directory)) {
				CloseConnection(connection);
				throw new ArgumentException("Directory does not exist", "directory");
			}

			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("File", new string[] { "Name" });
			query = queryBuilder.Where(query, "Directory", WhereOperator.Equals, "Directory");
			query = queryBuilder.OrderBy(query, new [] { "Name" }, new[] { Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(1);
			parameters.Add(new Parameter(ParameterType.String, "Directory", directory));

			DbCommand command = builder.GetCommand(connection, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<string> result = new List<string>(20);

				while(reader.Read()) {
					result.Add(directory + reader["Name"] as string);
				}

				CloseReader(command, reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Gets the outgoing links of a page.
		/// </summary>
		/// <param name="page">The full name of the page.</param>
		/// <returns>The outgoing links.</returns>
		/// <exception cref="ArgumentNullException">If <b>page</b> is <c>null</c>.</exception>
		/// <exception cref="ArgumentException">If <b>page</b> is empty.</exception>
		public string[] GetOutgoingLinks(string page) {
			if(page == null) throw new ArgumentNullException("page");
			if(page.Length == 0) throw new ArgumentException("Page cannot be empty", "page");

			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("OutgoingLink", new string[] { "Destination" });
			query = queryBuilder.Where(query, "Source", WhereOperator.Equals, "Source");
			query = queryBuilder.OrderBy(query, new[] { "Destination" }, new[] { Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(1);
			parameters.Add(new Parameter(ParameterType.String, "Source", page));

			DbCommand command = builder.GetCommand(connString, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<string> result = new List<string>(20);

				while(reader.Read()) {
					result.Add(reader["Destination"] as string);
				}

				CloseReader(command, reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Gets all the pages in a namespace that are bound to zero categories.
		/// </summary>
		/// <param name="nspace">The namespace (<c>null</c> for the root).</param>
		/// <returns>The pages, sorted by name.</returns>
		public PageInfo[] GetUncategorizedPages(NamespaceInfo nspace) {
			string nspaceName = nspace != null&&!string.IsNullOrEmpty(nspace.Name) ? nspace.Name : " ";

			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("Page", "CategoryBinding", "Name", "Page", Join.LeftJoin);
			query = queryBuilder.Where(query, "CategoryBinding", "Category", WhereOperator.IsNull, null);
			query = queryBuilder.AndWhere(query, "Page", "Namespace", WhereOperator.Equals, "Namespace");
			query = queryBuilder.OrderBy(query, new[] { "Name" }, new[] { Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(1);
			parameters.Add(new Parameter(ParameterType.String, "Namespace", nspaceName));

			DbCommand command = builder.GetCommand(connString, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<PageInfo> result = new List<PageInfo>(100);

				while(reader.Read()) {
					result.Add(new PageInfo(NameTools.GetFullName((reader["Namespace"] as string).Trim(), reader["Name"] as string),
						this, (DateTime)reader["CreationDateTime"]));
				}

				CloseReader(command, reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Gets all the Log Entries, sorted by date/time (oldest to newest).
		/// </summary>
		/// <returns>The Log Entries.</returns>
		public LogEntry[] GetLogEntries() {
			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("Log", new string[] { "DateTime", "EntryType", "User", "Message" });
			query = queryBuilder.OrderBy(query, new string[] { "DateTime" }, new Ordering[] { Ordering.Asc });

			DbCommand command = builder.GetCommand(connString, query, new List<Parameter>());

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<LogEntry> result = new List<LogEntry>(100);

				while(reader.Read()) {
					result.Add(new LogEntry(EntryTypeFromChar((reader["EntryType"] as string)[0]),
						(DateTime)reader["DateTime"], reader["Message"] as string, reader["User"] as string));
				}

				CloseReader(command, reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Gets the Backup/Revision numbers of a Page.
		/// </summary>
		/// <param name="connection">A database connection.</param>
		/// <param name="page">The Page to get the Backups of.</param>
		/// <returns>The Backup/Revision numbers.</returns>
		private int[] GetBackups(DbConnection connection, PageInfo page) {
			if(GetPage(connection, page.FullName) == null) {
				return null;
			}

			string name, nspace;
			NameTools.ExpandFullName(page.FullName, out nspace, out name);
			if( string.IsNullOrEmpty(nspace)||string.IsNullOrEmpty(nspace.Trim())) nspace = " ";

			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("PageContent", new string[] { "Revision" });
			query = queryBuilder.Where(query, "Page", WhereOperator.Equals, "Page");
			query = queryBuilder.AndWhere(query, "Namespace", WhereOperator.Equals, "Namespace");
			query = queryBuilder.AndWhere(query, "Revision", WhereOperator.GreaterThanOrEqualTo, "Revision");
			query = queryBuilder.OrderBy(query, new[] { "Revision" }, new[] { Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(3);
			parameters.Add(new Parameter(ParameterType.String, "Page", name));
			parameters.Add(new Parameter(ParameterType.String, "Namespace", nspace));
			parameters.Add(new Parameter(ParameterType.Int16, "Revision", FirstRevision));

			DbCommand command = builder.GetCommand(connection, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				List<int> result = new List<int>(100);

				while(reader.Read()) {
					result.Add((short)Convert.ChangeType(reader["Revision"],typeof(short)));
				}

				CloseReader(reader);

				return result.ToArray();
			}
			else return null;
		}
		/// <summary>
		/// Cuts the recent changes if necessary.
		/// </summary>
		private void CutRecentChangesIfNecessary() {
			ICommandBuilder builder = GetCommandBuilder();
			DbConnection connection = builder.GetConnection(connString);
			DbTransaction transaction = BeginTransaction(connection);

			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectCountFrom("RecentChange");

			DbCommand command = builder.GetCommand(transaction, query, new List<Parameter>());

			int rows = ExecuteScalar<int>(command, -1, false);

			int maxChanges = int.Parse(host.GetSettingValue(SettingName.MaxRecentChanges));

			if(rows > maxChanges) {
				// Remove 10% of old changes to avoid 1-by-1 deletion every time a change is made
				int entriesToDelete = maxChanges / 10;
				if(entriesToDelete > rows) entriesToDelete = rows;
				//entriesToDelete += entriesToDelete / 10;

				// This code is not optimized, but it surely works in most DBMS
				query = queryBuilder.SelectFrom("RecentChange", new string[] { "Id" });
				query = queryBuilder.OrderBy(query, new string[] { "Id" }, new Ordering[] { Ordering.Asc });

				command = builder.GetCommand(transaction, query, new List<Parameter>());

				DbDataReader reader = ExecuteReader(command);

				List<int> ids = new List<int>(entriesToDelete);

				if(reader != null) {
					while(reader.Read() && ids.Count < entriesToDelete) {
						ids.Add((int)Convert.ChangeType(reader["Id"],typeof(int)));
					}

					CloseReader(reader);
				}

				if(ids.Count > 0) {
					// Given that the IDs to delete can be many, the query is split in many chunks, each one deleting 50 items
					// This works-around the problem of too many parameters in a RPC call of Oracle
					// See also CutLog

					for(int chunk = 0; chunk <= ids.Count / MaxParametersInQuery; chunk++) {
						query = queryBuilder.DeleteFrom("RecentChange");
						List<string> parms = new List<string>(MaxParametersInQuery);
						List<Parameter> parameters = new List<Parameter>(MaxParametersInQuery);

						for(int i = chunk * MaxParametersInQuery; i < Math.Min(ids.Count, (chunk + 1) * MaxParametersInQuery); i++) {
							parms.Add("P" + i.ToString());
							parameters.Add(new Parameter(ParameterType.Int32, parms[parms.Count - 1], ids[i]));
						}

						query = queryBuilder.WhereIn(query, "Id", parms.ToArray());

						command = builder.GetCommand(transaction, query, parameters);

						if(ExecuteNonQuery(command, false) < 0) {
							RollbackTransaction(transaction);
							return;
						}
					}
				}
			}

			CommitTransaction(transaction);
		}
		/// <summary>
		/// Gets all the users that have the specified element in their data.
		/// </summary>
		/// <param name="key">The key of the data.</param>
		/// <returns>The users and the data.</returns>
		/// <exception cref="ArgumentNullException">If <b>key</b> is <c>null</c>.</exception>
		/// <exception cref="ArgumentException">If <b>key</b> is empty.</exception>
		public IDictionary<UserInfo, string> GetUsersWithData(string key) {
			if(key == null) throw new ArgumentNullException("key");
			if(key.Length == 0) throw new ArgumentException("Key cannot be empty", "key");

			ICommandBuilder builder = GetCommandBuilder();
			QueryBuilder queryBuilder = new QueryBuilder(builder);

			string query = queryBuilder.SelectFrom("User", "UserData", "Username", "User", Join.RightJoin,
				new string[] { "Username", "DisplayName", "Email", "Active", "DateTime" }, new string[] { "Data" },
				"UserGroupMembership", "User", Join.LeftJoin, new string[] { "UserGroup" });
			query = queryBuilder.Where(query, "UserData", "Key", WhereOperator.Equals, "Key");
			query = queryBuilder.OrderBy(query, new[] { "User_Username" }, new[] { Ordering.Asc });

			List<Parameter> parameters = new List<Parameter>(1);
			parameters.Add(new Parameter(ParameterType.String, "Key", key));

			DbCommand command = builder.GetCommand(connString, query, parameters);

			DbDataReader reader = ExecuteReader(command);

			if(reader != null) {
				Dictionary<UserInfo, string> result = new Dictionary<UserInfo, string>(100);

				string prevUsername = "******";
				UserInfo prevUser = null;
				string username = null;
				string displayName;
				string email;
				bool active;
				DateTime dateTime;
				string data;
				List<string> groups = new List<string>(5);

				while(reader.Read()) {
					username = reader["User_Username"] as string;

					if(username != prevUsername) {
						// Set previous user's groups
						if(prevUsername != "|||") {
							prevUser.Groups = groups.ToArray();
							groups.Clear();
						}

						// Read new data
						displayName = GetNullableColumn<string>(reader, "User_DisplayName", null);
						email = reader["User_Email"] as string;
						active = (bool)reader["User_Active"];
						dateTime = (DateTime)reader["User_DateTime"];
						data = reader["UserData_Data"] as string;

						// Append new user
						prevUser = new UserInfo(username, displayName, email, active, dateTime, this);
						result.Add(prevUser, data);
					}

					// Keep reading groups
					prevUsername = username;
					if(!IsDBNull(reader, "UserGroupMembership_UserGroup")) {
						groups.Add(reader["UserGroupMembership_UserGroup"] as string);
					}
				}

				if(prevUser != null) {
					prevUser.Groups = groups.ToArray();
				}

				CloseReader(command, reader);

				return result;
			}
			else return null;
		}