C# Strange Index Out Of Bounds exception

Question

I have a strange problem with an Index Out of Bounds exception when debugging an addin I am developing for MS Outlook 2010. I have a class to make message processing and in the constructor for that class, I pass a MailItem. I then intend to run through the Recipients list of the MailItem, and find all recipients registered in the To, CC, and BCC fields. For this I have the following code:

public MessageProcessor(Outlook.MailItem theMail)
{
  _activeMailItem = theMail;
  _activeMailDetails.Sender = theMail.SenderEmailAddress;
  if (_activeMailItem.Recipients.Count > 0)
  {
    List<string> recipients = new List<string>();
    List<string> cc = new List<string>();
    List<string> bcc = new List<string>();
    for (int i = 0; i < _activeMailItem.Recipients.Count; i++)
    {
      switch (_activeMailItem.Recipients[i].Type)    <----- HERE
      {
        case (int)Outlook.OlMailRecipientType.olTo:
           recipients.Add(_activeMailItem.Recipients[i].Address);
           break;
        case (int)Outlook.OlMailRecipientType.olCC:
           cc.Add(_activeMailItem.Recipients[i].Address);
           break;
        case (int)Outlook.OlMailRecipientType.olBCC:
           bcc.Add(_activeMailItem.Recipients[i].Address);
           break;
      }
    }
  }
}

However, I get the exception at the point marked "HERE". When I debug and look at the value of the Recipients.Count property, it shows 1. However, the problem occurs when the "i" index is 0 (which should be a valid index - and, in this case, the only valid index). When I try to look at the _activeMailItem.Recipients collection, I see the Count of 1; however, when I try to track further down in the structure, I see some red crosses, and I can't inspect the values below that.

Does anyone have a clue about what can be wrong?

Thanks in advance.

Answer 1

All collections in Outlook (including Recipients) are 1 based, not 0:

for (int i = 1; i <= _activeMailItem.Recipients.Count; i++)