/*
 * Berkeley DB XML .NET API
 * 
 * Copyright (C) 2007 Jana Business Consulting Ltd. All rights reserved.
 * 
 * For more information, see http://www.janabiz.com.
 * 
 */

using System;
using JanaBiz.Db;
using JanaBiz.DbXml;
using JanaBiz.DbXml.Exceptions;

public class DeleteDocument
{
    private static string theContainer = "namespaceExampleData.dbxml";

    // Method that deletes all documents from a DB XML container that match a given
    // XQuery.
    private static void doDeleteDocument(XmlManager mgr, XmlContainer container,
                                         string query, XmlQueryContext context, XmlTransaction txn)
    {
        Console.WriteLine("Deleting documents for expression: '" + query + "'.");
        Console.WriteLine("Return to continue: ");
        Console.ReadLine();

        // Perform our query. We'll delete any document contained in this result set.
        XmlResults results = mgr.Query(txn, query, context, new XmlDocumentConfig());
        Console.WriteLine("Found " + results.Size +
                          " matching the expression '" + query + "'.");

        // Get an update context.
        using (XmlUpdateContext updateContext = mgr.CreateUpdateContext()) {
            while (results.MoveNext()) {
                XmlDocument document = results.Current.ToDocument();

                string name = document.Name;
                Console.WriteLine("Deleting document: " + name + ".");

                // Peform the delete
                container.DeleteDocument(txn, document, updateContext);
                Console.WriteLine("Deleted document: " + name + ".");
            }
        }
    }

    // Utility method that we use to make sure the documents that we thought 
    // were deleted from the container are in fact deleted. 
    private static void confirmDelete(XmlManager mgr, string query, XmlQueryContext context)
    {
        Console.WriteLine("Confirming the delete.");
        Console.WriteLine("The query: '" + query +
                          "' should return result set size 0.");
        XmlResults results = mgr.Query(null, query, context, new XmlDocumentConfig());
        if (results.Size == 0) {
            Console.WriteLine("Result set size is 0. Deletion confirmed.");
        } else {
            Console.WriteLine("Result set size is " + results.Size +
                              ". Deletion failed.");
        }
    }

    public static void Main(string[] args)
    {
        string envdir = parseArguments(args);

        DbEnvironment dbEnv = null;
        XmlManager mgr = null;
        XmlContainer container = null;

        try {
            // Open an environment 
            dbEnv = CreateDbEnvironment(envdir);

            // Open a manager
            using (mgr = CreateManager(dbEnv)) {
                // Open a transactional container
                XmlContainerConfig containerconfig = new XmlContainerConfig();
                containerconfig.Transactional = true;
                using (container = mgr.OpenContainer(null, theContainer,
                                                     containerconfig)) {
                    // Start a transaction
                    using (XmlTransaction txn = mgr.CreateTransaction()) {
                        // Create a context and declare the namespaces
                        using (XmlQueryContext context = mgr.CreateQueryContext()) {
                            context.SetNamespace("fruits", "http://groceryItem.dbxml/fruits");
                            context.SetNamespace("vegetables", "http://groceryItem.dbxml/vegetables");
                            context.SetNamespace("desserts", "http://groceryItem.dbxml/desserts");

                            // Delete the document that describes Mabolo (a fruit)
                            string query = "collection(\"" + theContainer + "\")/fruits:item[product = 'Mabolo']";

                            // If doDeleteDocument throws an exception then the using block
                            // will call Dispose() on the Transaction, which will cause it
                            // to abort itself.
                            doDeleteDocument(mgr, container, query, context, txn);
                            txn.Commit();

                            confirmDelete(mgr, query, context);
                        }
                    }
                }
            }
        } catch (DbXmlException e) {
            Console.WriteLine("Error performing document delete against " + theContainer);
            Console.WriteLine(e.ToString());
        } finally {
            if (container != null) {
                container.Close();
            }
            if (mgr != null) {
                mgr.Close();
            }
            if (dbEnv != null) {
                dbEnv.Close();
            }
        }
    }

    public static DbEnvironment CreateDbEnvironment(string envdir)
    {
        DbEnvironmentConfig envconf = new DbEnvironmentConfig();
        envconf.CacheSize = 50*1024;
        envconf.AllowCreate = true;
        envconf.InitializeCache = true;
        envconf.Transactional = true;
        envconf.InitializeLocking = true;
        envconf.InitializeLogging = true;
        envconf.RunRecovery = true;
        envconf.ErrorWriter = Console.Out;
        envconf.ErrorPrefix = "LOG";

        DbEnvironment env = new DbEnvironment(envdir, envconf);

        return env;
    }

    public static XmlManager CreateManager(DbEnvironment env)
    {
        XmlManagerConfig mgrconfig = new XmlManagerConfig();
        mgrconfig.AdoptEnvironment = true;

        try {
            return new XmlManager(env, mgrconfig);
        } catch (Exception e) {
            env.Close();
            throw e;
        }
    }

    private static void Usage()
    {
        Console.WriteLine("This program deletes an XML document from a DBXML container.");
        Console.WriteLine("You should run exampleLoadContainer before running this example.");
        Console.WriteLine("You are only required to pass this command the path location of the");
        Console.WriteLine("database environment that you specified when you loaded the examples data:");
        Console.WriteLine();
        Console.WriteLine("\t-h <dbenv directory>");
        Console.WriteLine("For example:");
        Console.WriteLine("\tdeleteDocument.exe -h examplesEnvironment");

        Environment.Exit(-1);
    }

    private static string parseArguments(string[] args)
    {
        string envdir = null;
        for (int i = 0; i < args.Length; ++i) {
            string arg = args[i];
            if ((arg.StartsWith("-")
#if WIN32
                 || arg.StartsWith("/")
#endif
                ) && arg.Length > 1) {
                switch (arg[1]) {
                    case 'h':
                        {
                            ++i;
                            if (i >= args.Length) {
                                Console.WriteLine("Invalid option: " + arg);
                                Usage();
                            }
                            envdir = args[i];
                            break;
                        }
                    default:
                        {
                            Console.WriteLine("Unknown option: " + arg);
                            Usage();
                            break;
                        }
                }
            } else {
                Console.WriteLine("Too many arguments: " + arg);
                Usage();
            }
        }
        if (envdir == null) {
            Console.WriteLine("Environment directory not found.");
            Usage();
        }
        return envdir;
    }
}

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