遍历邮件分类，并显示分类颜色

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Office.Tools.Ribbon;
using Outlook = Microsoft.Office.Interop.Outlook;
using System.Windows.Forms;

namespace OutlookAddIn20
{
    public partial class Ribbon1
    {
        private void Ribbon1_Load(object sender, RibbonUIEventArgs e)
        {
        }

        private void button1_Click(object sender, RibbonControlEventArgs e)
        {
            Outlook.Application objApplication = Globals.ThisAddIn.Application;
            Outlook.NameSpace objSession = objApplication.Session;
            Outlook.Categories objCategories = objSession.Categories;
            try
            {
                Outlook.MailItem objMailItem = objApplication.ActiveExplorer().Selection[1] as Outlook.MailItem;
                if (objMailItem != null)
                {
                    if (objMailItem.Categories != null)
                    {
                        string[] strCategories = objMailItem.Categories.Split(',');
                        foreach (string strCategory in strCategories)
                        {
                            Outlook.Category objCategory = objCategories[strCategory.Trim()];   //这一步非常重要，在有多个分类的情况下每个分类间有“, ”隔开。在使用时必须先去掉前导空格。
                            MessageBox.Show(objCategory.Color.ToString());
                        }
                    }
                    else
                    {
                        MessageBox.Show("There no flag");
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message+"\n"+ex.StackTrace);
            }
        }
    }
}

实现环境：Visual Studio 2010, Outlook 2010, .Net Framework 4.0, VSTO runtime 4.0