Unable to cast COM object of type 'System.__ComObject' to interface type 'Microsoft.Office.Interop.Outlook.ContactItem'.

[Silvia]

Hi,

I get the following error after deploying my Word Document add-in. The Addin
retrieves Outlook Contacts and add's
them to a Word template. Everything works fine on my development machine.

Unable to cast COM object of type 'System.__ComObject' to interface type
'Microsoft.Office.Interop.Outlook.ContactItem'.

This is the code:
//contacten ophalen uit Outlook en in Datatable zetten
Outlook.Application oApp = new
Microsoft.Office.Interop.Outlook.Application();

Outlook.NameSpace ns = oApp.Session;
ns.Logon(Missing.Value, Missing.Value, false, true);

Outlook.MAPIFolder oContacts;
Outlook.Items oItems;

Outlook.MAPIFolder RootContactsFolder =
ns.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderContacts);
string RootFolder = RootContactsFolder.Name;

if ((folder == "") || (folder == RootFolder))
{
// Get the default Contacts folder.
oContacts = RootContactsFolder;
// Get the Items collection from the folder.
oItems = oContacts.Items;
}
else
{
//contactpersonen uit submap halen en foldernaam meegeven
oContacts = RootContactsFolder;
oItems = oContacts.Items;

}

DataTable _dt = new DataTable("OutlookContacts");
_dt.Columns.Add("Title");
_dt.Columns.Add("FirstName");
_dt.Columns.Add("LastName");
_dt.Columns.Add("CompanyName");
_dt.Columns.Add("BusinessAddressStreet");
_dt.Columns.Add("BusinessAddressPostalCode");
_dt.Columns.Add("BusinessAddressCity");
_dt.Columns.Add("BusinessAddressCountry");
_dt.Columns.Add("Email");

//contactpersonen toevoegen aan datatable en teruggeven.
try
{
foreach (Outlook.ContactItem OlContact in oItems)
{

_dt.Rows.Add(OlContact.Title, OlContact.FirstName,
OlContact.LastName, OlContact.CompanyName,
OlContact.BusinessAddressStreet,
OlContact.BusinessAddressPostalCode,
OlContact.BusinessAddressCity,
OlContact.BusinessAddressCountry,
OlContact.Email1Address);
}
return _dt;
}
catch (Exception e)
{
MessageBox.Show(e.Message);
return null;
}

Regards Silvia

[Scott Welker]

Hi Silvia, without carefully studying your code, this seems reminiscent of
the Exchange Server RPC channel limit. See if the failure occurs at or around
the 250th iteration. If so, I'll bet you've hit this too little
published/documented limitation.

As Ken Slovak, MVP - Outlook explained it to me, each object you create
opens an RPC connection to the exchange server and that connection may not be
released until the method/scope ends or you explicitly release the object. I
fixed my problem with code like the following:

Pseudo/real code
…iterator code (i) - over the Outlook.MAPIFolder. myItem is an
Outlook.PostItem (ContactItem' in your case) , from the folder's Items
collection

//Do your stuff...

// Resource Cleanup
System.Runtime.InteropServices.Marshal.ReleaseComObject(myItem);
if (i % 200 == 0) // Force garbage collection after every 200 items
{
GC.Collect();
}
… end iterator

Good luck!!