Corrupted MS Word/Excel file after File.OpenWrite

Question

I am attempting to programatically update or create a MS Word or Excel file on a shared drive if the ContentLength does not match. The file is originally stored in a Sharepoint Database. I am able to do this successfully when the file is written to a local directory, however, when this is done to a file on a network drive, even though the file is rewritten, the content becomes corrupted and is unable to be opened properly.

I'm not sure if the issue lies in the WriteFile() and there is a better way to create or update an Excel/Word file using something other than File.Write and file.OpenWrite

My code is as follows:

public void UpsertSharepointFiles()
        {
            try
            {



  var spList = GetSharepointDirectories();

            var targetDir = @"\\111.111.0.11\c$\websites\XXX\FormLibrary";

            IntPtr token = IntPtr.Zero;
            bool valid = LogonUser("administrator",
                        "XXX",
                        "XXX",
                        (int)LogonType.NewCredentials,
                        (int)LogonProvider.WinNT50,
                        ref token);

            if (valid)
            {

                using (WindowsImpersonationContext context = WindowsIdentity.Impersonate(token))
                {

                    CloseHandle(token);

                    //var targetDir = Server.MapPath("~/TempCopy");
                    //var targetDir = @"\\\\222.222.2.22\c$\websites\XXX\FormLibrary";
                    var targetDirInfo = new DirectoryInfo(targetDir);

                    var dirs = targetDirInfo.GetDirectories("*.*", SearchOption.AllDirectories);

                    if (spList != null)
                    {

                        foreach (var spFile in spList)
                        {
                            if (spFile.Content != null)
                            {
                                foreach (var dir in dirs)
                                {
                                    var searchFile = dir.GetFiles(spFile.LeafName);
                                    var currDirName = dir.Name;

                                    if (currDirName == "ABBH")
                                    {
                                        currDirName = "ABB";
                                    }

                                    if (searchFile.Count() == 0) //Web Server - No, SP - Yes
                                    {
                                        CreateFileOnWebServer(currDirName, spFile, targetDir);
                                    }
                                    else // Web Server - Yes, SP - Yes
                                    {
                                        UpdateFileOnWebServer(searchFile, spFile, targetDir, currDirName);
                                    }
                                }

                            }
                        }

                        foreach (var dir in dirs)
                        {
                            DeleteFilesOnWebServerNotInSharepointDb(dir, spList);
                        }
                    }
                }

                lblSuccessMessage.Text = "Forms Library in Website successfully synced with Sharepoint Forms Library!";
                lblSuccessMessage.Visible = true;
            }
        }
        catch (Exception)
        {
            lblErrorMessage.Text = "Error occurred when syncing Forms Library in Website.  Please try again.";
            lblErrorMessage.Visible = true;
        }

    }

private static void DeleteFilesOnWebServerNotInSharepointDb(DirectoryInfo dir, List<SharepointVO> spList)
        {
            var dirFileList = dir.GetFiles();

            var filesOnServerNotInSharepointDb = dirFileList.Where(w => spList.All(s => s.LeafName != w.Name));
            foreach (var file in filesOnServerNotInSharepointDb)
            {
                var fInfo = new FileInfo(file.DirectoryName + @"\" + file.Name).ToString();
                System.IO.File.Delete(fInfo);
            }
        }

        private static void UpdateFileOnWebServer(FileInfo[] searchFile, SharepointVO spFile, string targetDir,
            string currDirName)
        {
            if (searchFile[0].Directory.Name == spFile.Directory)
            {
                // Replace file with Sharepoint file
                if (spFile.ContentLength != searchFile[0].Length) //Checks only first file
                {
                    WriteFile(currDirName, spFile, targetDir);
                }
            }
        }

        private static void CreateFileOnWebServer(string currDirName, SharepointVO spFile, string targetDir)
        {
            if (currDirName == spFile.Directory)
            {
                // Check if directory exists on server
                if (Directory.Exists(targetDir + "/" + currDirName))
                {
                    {
                        {
                            WriteFile(currDirName, spFile, targetDir);
                        }
                    }
                }
                else
                {
                    Directory.CreateDirectory(targetDir + "/" + currDirName);

                    WriteFile(currDirName, spFile, targetDir);
                }
            }
        }

        private static void WriteFile(string currDirName, SharepointVO spFile, string targetDir)
        {
            using (
                Stream fs =
                    System.IO.File.OpenWrite(targetDir + "/" + currDirName + "/" + spFile.LeafName))
            {
                fs.Write(spFile.Content, 0, spFile.Content.Length);
            }
        }

        [DllImport("advapi32.dll", SetLastError = true)]
        public static extern bool LogonUser(string lpszUsername, string lpszDomain, string lpszPassword, int dwLogonType, int dwLogonProvider, ref IntPtr phToken);

        [DllImport("kernel32.dll")]
        public static extern bool CloseHandle(IntPtr token);

        enum LogonType
        {
            Interactive = 2,
            Network = 3,
            Batch = 4,
            Service = 5,
            Unlock = 7,
            NetworkClearText = 8,
            NewCredentials = 9
        }

        enum LogonProvider
        {
            Default = 0,
            WinNT35 = 1,
            WinNT40 = 2,
            WinNT50 = 3
        }