Question

We are developing Outlook 2007 add-in. For testing outlook category renaming I’ve added the following code block

 var session = Application.Session;
 var categories = session.Categories;
 var category1 = session.Categories[1];

 //catefory1.Name is "Group1" before executing line below
 category1.Name = "TEST!!!";

 Marshal.ReleaseComObject(category1);
 Marshal.ReleaseComObject(categories);
 Marshal.ReleaseComObject(session);

to the end of add-in private void ThisAddIn_Startup(object sender, EventArgs e) method.
Category is renamed but if Outlook is closed, the above lines are commented, and outlook is started again – the category name is not “TEST!!!” as I expected. It is “Group1” as is was before renaming. Is it possible to rename outlook category “forever” by code? Microsoft.Office.Interop.Outlook.Category has no Save() or Update() or Persist() methods.

P.S. We are developing Outlook 2007 add-in using Visual Studio 2008, .net 3.5, C# 3.
The problem is reproduced with Outlook 2007 SP1 and SP2. Other outlook versions were not tested.

Answer 1

I have solved the problem (the problem itself seems to be Outlook 2007 bug) using a hack.
The following links helped me to create the hack (oops, not enough reputation to post more then 1 link):

• http ://blogs.officezealot.com/legault/archive/2009/08/13/21577.aspx
• http://www.officekb.com/Uwe/Forum.aspx/outlook-prog-addins/3142/Apply-Categories-to-other-users-Outlook-2007
• http ://help.wugnet.com/office/set-master-category-list-Outlook-2007-ftopict1095935.html
• http ://forums.slipstick.com/showthread.php?t=18189
• http ://msdn.microsoft.com/en-us/library/ee203806%28EXCHG.80%29.aspx

The hack itself is show below:

using System;
using System.Text;
using System.Xml;
using System.IO;
using Microsoft.Office.Interop.Outlook;

namespace OutlookHack
{
    public static class OutlookCategoryHelper
    {
        private const string CategoryListStorageItemIdentifier = "IPM.Configuration.CategoryList";
        private const string CategoryListPropertySchemaName = @"http://schemas.microsoft.com/mapi/proptag/0x7C080102";
        private const string CategoriesXmlElementNamespace = "CategoryList.xsd";
        private const string XmlNamespaceAttribute = "xmlns";
        private const string CategoryElement = "category";
        private const string NameAttribute = "name";

        public static void RenameCategory(string oldName, string newName, Application outlookApplication)
        {
            MAPIFolder calendarFolder = outlookApplication.Session.GetDefaultFolder(
                OlDefaultFolders.olFolderCalendar);
            StorageItem categoryListStorageItem = calendarFolder.GetStorage(
                CategoryListStorageItemIdentifier, OlStorageIdentifierType.olIdentifyByMessageClass);

            if (categoryListStorageItem != null)
            {
                PropertyAccessor categoryListPropertyAccessor = categoryListStorageItem.PropertyAccessor;
                string schemaName = CategoryListPropertySchemaName;
                try
                {
                    // next statement raises Out of Memory error if property is too big
                    var xmlBytes = (byte[])categoryListPropertyAccessor.GetProperty(schemaName);

                    // the byte array has to be translated into a string and then the XML has to be parsed
                    var xmlReader = XmlReader.Create(new StringReader(Encoding.UTF8.GetString(xmlBytes)));

                    // xmlWriter will write new category list xml with renamed category
                    XmlWriterSettings settings = new XmlWriterSettings { Indent = true, IndentChars = ("\t") };
                    var stringWriter = new StringWriter();
                    var xmlWriter = XmlWriter.Create(stringWriter, settings);

                    xmlReader.Read(); // read xml declaration
                    xmlWriter.WriteNode(xmlReader, true);
                    xmlReader.Read(); // read categories
                    xmlWriter.WriteStartElement(xmlReader.Name, CategoriesXmlElementNamespace);
                    while (xmlReader.MoveToNextAttribute())
                    {
                        if (xmlReader.Name != XmlNamespaceAttribute) // skip namespace attr
                        {
                            xmlWriter.WriteAttributeString(xmlReader.Name, xmlReader.Value);
                        }
                    }
                    while (xmlReader.Read())
                    {
                        switch (xmlReader.NodeType)
                        {
                            case XmlNodeType.Element: // read category
                                xmlWriter.WriteStartElement(CategoryElement);
                                while (xmlReader.MoveToNextAttribute())
                                {
                                    if ((xmlReader.Name == NameAttribute) && (xmlReader.Value == oldName))
                                    {
                                        xmlWriter.WriteAttributeString(NameAttribute, newName);
                                    }
                                    else
                                    {
                                        xmlWriter.WriteAttributeString(xmlReader.Name, xmlReader.Value);
                                    }
                                }
                                xmlWriter.WriteEndElement();
                                break;
                            case XmlNodeType.EndElement: // categories ended
                                xmlWriter.WriteEndElement();
                                break;
                        }
                    }
                    xmlReader.Close();
                    xmlWriter.Close();

                    xmlBytes = Encoding.UTF8.GetBytes(stringWriter.ToString());
                    categoryListPropertyAccessor.SetProperty(schemaName, xmlBytes);
                    categoryListStorageItem.Save();
                }
                catch (OutOfMemoryException)
                {
                    // if error is "out of memory error" then the XML blob was too big
                }
            }
        }
    }
}

This helper method must be called prior to category renaming, e.g.:

 var session = Application.Session;
 var categories = session.Categories;
 var category1 = session.Categories[1];

 //catefory1.Name is "Group1" before executing line below
 OutlookCategoryHelper.RenameCategory(category1.Name, "TEST!!!", Application);
 category1.Name = "TEST!!!";

 Marshal.ReleaseComObject(category1);
 Marshal.ReleaseComObject(categories);
 Marshal.ReleaseComObject(session);