Using the Microsoft Desktop Stack – Part 3: Using Entity Framework 4 in an MVVM Application

using System;
using System.IO;
using System.Reflection;
using log4net;

namespace MsDesktopStackDemo.Services
{
    /// <summary>
    /// Provides file services to the application.
    /// </summary>
    public class FileServices
    {
        #region Fields

        // Member variables
        private static readonly ILog m_Logger = LogManager.GetLogger("FileServices");

        #endregion

        #region Public Methods

        /// <summary>
        /// Gets a file path to the data file for this app.
        /// </summary>
        /// <returns>A file path to the data file for this app.</returns>
        public static string GetDataFilePath()
        {
            // Log invocation
            m_Logger.Info("FileServices.GetDataFilePath() invoked.");

            /* If the app was installed on this machine using the Installer project 
             * included in the demo, then the data file (Books.sdf) was copied to the 
             * Windows CommonDocuments folder on install. If the app is running from 
             * source code in Visual Studio, then the app was copied to the application 
             * output folder on compile. So, we check both locations for the data file. */

            // Initialize
            string dataFilePath;

            // Search Windows CommonDocuments folder for data file
            var foundFile = SearchCommonDocumentsFolder(@"MsDesktopStackDemo\Books.sdf", out dataFilePath);

            // Search application output folder for data file
            if (! foundFile)
            {
                foundFile = SearchApplicationOutputFolder("Books.sdf", out dataFilePath);
            }

            // If file not found in either location, throw exception
            if (!foundFile)
            {
                var errMsg = "Data file 'Books.sdf' was not found.";
                m_Logger.Error(errMsg);
                throw new ApplicationException(errMsg);
            }

            // Log completion
            m_Logger.Info("FileServices.GetDataFilePath() completed.");

            //Set return value
            return dataFilePath;
        }

        /// <summary>
        /// Gets a file path to the folder containing the cover art used by this app.
        /// </summary>
        /// <returns>A file path to the folder containing the cover art used by this app.</returns>
        public static string GetCoversFolderPath()
        {
            // Log invocation
            m_Logger.Info("FileServices.GetCoversFolderPath() invoked.");

            /* We have to search both the Windows CommonDocuments folder and the
             * application output folderfor the cover art folder. See comments to 
             * GetDataFilePath(). */

            // Initialize
            string coverFilePath;

            /* We will search for the folder by searching for a file that should be in 
             * the folder. If we find the file, we have found the folder. I wouldn't
             * do this in a production app--I would test for the folder explicitly. But
             * doing things this way simplifies things for the demo. */

            // Search Windows CommonDocuments folder for data file
            var foundFile = SearchCommonDocumentsFolder(@"MsDesktopStackDemo\Covers\Flatlander.png", out coverFilePath);

            // Search application output folder for data file
            if (!foundFile)
            {
                foundFile = SearchApplicationOutputFolder(@"Covers\Flatlander.png", out coverFilePath);
            }

            // If file not found in either location, throw exception
            if (!foundFile)
            {
                var errMsg = "Cover art folder was not found.";
                m_Logger.Error(errMsg);
                throw new ApplicationException(errMsg);
            }

            // Get folder path from found file
            var coversFolderPath = Path.GetDirectoryName(coverFilePath);
            m_Logger.Info(String.Format("Cover art folder path: {0}", coversFolderPath));

            // Log completion
            m_Logger.Info("FileServices.GetDataFilePath() completed.");

            // Set return value
            return coversFolderPath;
        }
        
        #endregion

        #region Private Methods

        /// <summary>
        /// Searches the Windows CommonDocuments folder for a named file.
        /// </summary>
        /// <param name="fileSpec">The file to search for. Can be either a name or a partial path.</param>
        /// <param name="path">The path tested by the method.</param>
        /// <returns>True if the file was found; false otherwise.</returns>
        private static bool SearchCommonDocumentsFolder(string fileSpec, out string path)
        {
            // Log invocation
            m_Logger.Info("FileServices.SearchCommonDocumentsFolder() invoked.");

            // Look for file in Windows CommonDocuments folder
            var commonDocsPath = Environment.GetFolderPath(Environment.SpecialFolder.CommonDocuments);
            path = Path.Combine(commonDocsPath, fileSpec);
            var foundFile = File.Exists(path);

            // Log result
            string s = foundFile ? String.Empty : " not";
            string resultMsg  = String.Format("File '{0}'{1} found in Windows CommonDocuments folder.", fileSpec, s);
            m_Logger.Info(resultMsg);

            // Log completion
            m_Logger.Info("FileServices.SearchCommonDocumentsFolder() completed.");

            // Set return value
            return foundFile;
        }

        /// <summary>
        /// Searches the application output folder for a named file.
        /// </summary>
        /// <param name="fileSpec">The file to search for. Can be either a name or a partial path.</param>
        /// <param name="path">The path tested by the method.</param>
        /// <returns>True if the file was found; false otherwise.</returns>
        private static bool SearchApplicationOutputFolder(string fileSpec, out string path)
        {
            // Log invocation
            m_Logger.Info("FileServices.SearchApplicationOutputFolder() invoked.");

            // Get application output folder
            var appOutputFolder = Path.GetDirectoryName(Assembly.GetEntryAssembly().Location);
            if(appOutputFolder == null)
            {
                var errMsg = "Application output path returned null.";
                m_Logger.Error(errMsg);
                throw new ApplicationException(errMsg);
            }
            // Look for file in application output folder
            path = Path.Combine(appOutputFolder, fileSpec);
            var foundFile = File.Exists(path);

            // Log result
            string s = foundFile ? String.Empty : " not";
            string resultMsg = String.Format("File '{0}'{1} found in application output folder.", fileSpec, s);
            m_Logger.Info(resultMsg);

            // Log completion
            m_Logger.Info("FileServices.SearchApplicationOutputFolder() completed.");

            // Set return value
            return foundFile;
        }

        #endregion

    }
}