从Outlook删除Item时必须从后往前删

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.Diagnostics;
using System.Threading;

namespace MyThread
{
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 objNameSpace = objApplication.Session;
Outlook.MAPIFolder objInbox = objNameSpace
.Stores["**********"].GetRootFolder()
.Folders["******"];
int c = objInbox.Items.Count;
for (int i = c ; i > 0; i--)
{
var obj = objInbox.Items[i];
if (obj is Outlook.MailItem)
{
Outlook.MailItem objMailItem = (Outlook.MailItem)obj;
objMailItem.Delete();
Debug.Print(i.ToString());
Thread.Sleep(500);
}
}
}
}
}