Unable to cast COM object" error

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R

RW1yYWs

Hey all, I receive the following error:

Unable to cast COM object of type 'System.__ComObject' to interface type

'Microsoft.Office.Interop.Outlook._MailItem'.

I will demonstrate the 3 main attempts (of the trillion I've tried). :-/

Attempt #1:

oOutlook = new Outlook.Application();

oNs = oOutlook.GetNamespace("MAPI");

oFldr = oNs.Folders["Public Folders"].Folders["Test"]

foreach (MailItem oMessage in oFldr.Items)

{

> ...

}

Attempt #2:

oOutlook = new Outlook.Application();

oNs = oOutlook.GetNamespace("MAPI");

oFldr = oNs.Folders["Public Folders"].Folders["Test"]

foreach (Object oMessage in oFldr.Items)

{

> ...

}

Attempt #3:

oOutlook = new Outlook.Application();

oNs = oOutlook.GetNamespace("MAPI");

oFldr = oNs.Folders["Public Folders"].Folders["Test"]

for (int i = 1; i <= oFldr.Items.Count; i++)

{

Object o = oFldr.Items;

Type t = o.GetType();

}

I know that people are wont to send in email types other than MailItem. For

instance, there are several "discussion" items in the email box in question.

I've tried to isolate those, but when I run #3, I find that "oFldr.Items"

has a type of "System.__ComObject" which is unhelpful to me. All I'm trying

to do is grab email messages and discussion items and process them.

Unfortunately, it bombs out.

Help!
 
K

Ken Slovak - [MVP - Outlook]

Don't multipost. Also, always post your Outlook version.

You need to do a logon to NameSpace if you are using this code in a

standalone appliation. If it's a COM addin use the application object passed

to you in your connection handler. You also need to refer to the Public

Folders tree correctly.

object _missing = System.Reflection.Missing.Value;

oOutlook = new Outlook.Application();

oNs = oOutlook.GetNamespace("MAPI");

oNs.Logon(_missing, _missing, _missing, _missing);

oFldr =

oNs.GetDefaultFolder(Outlook.OlDefaultFolders.olPublicFoldersAllPublicFolders

).Folders["Test"];

for (int i = 1; i <= oFldr.Items.Count; i++)

{

Object o = oFldr.Items;

object[] args = new Object[] { };

Type t = o.GetType();

object retVal = o.InvokeMember("Class", BindingFlags.Public |

BindingFlags.GetField |

BindingFlags.GetProperty, null, o, args);

Outlook.OlObjectClass itemClass = (Outlook.OlObjectClass)retVal;

if (itemClass == Outlook.OlObjectClass.olNote)

{

// it's a mail item

Outlook.MailItem oMail = (Outlook.MailItem)o;

}

}

There are plenty of Outlook code samples in C# at www.outlookcode.com, my

Web site, the MS Office Developer Web site and many other places. It might

be helpful to you to study some of the code to see how things are done.

What I showed has no error handling, something especially needed in managed

code.

"Emrak" <Emrak> wrote in message

news:568EA84A-0B4A-4C13-AB07-9E0D218B1296@microsoft.com...
> Hey all, I receive the following error:
> Unable to cast COM object of type 'System.__ComObject' to interface type
> 'Microsoft.Office.Interop.Outlook._MailItem'.

> I will demonstrate the 3 main attempts (of the trillion I've tried). :-/

> Attempt #1:
> oOutlook = new Outlook.Application();
> oNs = oOutlook.GetNamespace("MAPI");
> oFldr = oNs.Folders["Public Folders"].Folders["Test"]

> foreach (MailItem oMessage in oFldr.Items)
> {
> ...
> }

> Attempt #2:
> oOutlook = new Outlook.Application();
> oNs = oOutlook.GetNamespace("MAPI");
> oFldr = oNs.Folders["Public Folders"].Folders["Test"]

> foreach (Object oMessage in oFldr.Items)
> {
> ...
> }

> Attempt #3:
> oOutlook = new Outlook.Application();
> oNs = oOutlook.GetNamespace("MAPI");
> oFldr = oNs.Folders["Public Folders"].Folders["Test"]

> for (int i = 1; i <= oFldr.Items.Count; i++)
> {
> Object o = oFldr.Items;
> Type t = o.GetType();
> }

> I know that people are wont to send in email types other than MailItem.
> For
> instance, there are several "discussion" items in the email box in
> question.
> I've tried to isolate those, but when I run #3, I find that
> "oFldr.Items"
> has a type of "System.__ComObject" which is unhelpful to me. All I'm
> trying
> to do is grab email messages and discussion items and process them.
> Unfortunately, it bombs out.

> Help!
 
R

RW1yYWs

Good day Mr Slovak,

My apologies for the multipost. Desperation isn't just an 11-letter word.

I have most definitely explored many, many of the programmatic solutions

available online.

My Outlook version is 2003, SP3.

I appreciate your code sample. My main problem at this point (what it has

always been, actually) is not so much handling the "MailItem" objects, but

handling the "discussion" objects. How do I reference them, specifically?

Olnote references only MailItems and not discussions. The bulk of email

received is in a "discussion" format.

Thanks much for your assistance.
 
R

RW1yYWs

As an addendum to my last post, I've learned that "Post" is the object type

I'm looking for. As such, I'll demonstrate my current solution for posterity.

I'm using the KISS method here. This works, but I can't determine how, in the

context of "string filter" below, how I'm supposed to code "OR" below. For

instance, MessageClass = NOTE OR POST.

//instanciate variables

Microsoft.Office.Interop.Outlook.Application oOutlook;

Microsoft.Office.Interop.Outlook.NameSpace oNs;

Microsoft.Office.Interop.Outlook.MAPIFolder oFldr;

int iAttachCnt = 0;

oOutlook = new Microsoft.Office.Interop.Outlook.Application();

oNs = oOutlook.GetNamespace("MAPI");

//are there any emails to process?

oFldr = oNs.Folders["Public Folders"].Folders["Test"]

if (oFldr.Items.Count > 0)

{

//cycle through each email, filtering out only messages and posts, no

calendars or tasks

string filter = "[MessageClass] = \"IPM.Note\"";

Microsoft.Office.Interop.Outlook.Items oTestItems =

oFldr.Items.Restrict(filter);

> ...

}
 
R

RW1yYWs

I am making the assumption as of now (tell me if I'm wrong), that I can only

process Posts and Notes separately. I thank you for your time.
 
K

Ken Slovak - [MVP - Outlook]

You can filter or restrict on both Note and Post items in the same filter.

Obviously when you retrieve an Object that could be either you further need

to test for either Class or MessageClass to know which type to assign that

Object.

However, unless you don't have any possibility of running into custom forms

or want to exclude all custom forms you are probably best off using a filter

that checks for the MessageClass starting with "IPM.Note" or starting with

"IPM.Post". That's easiest to do using the undocumented capability of using

SQL type statements in a filter.

That filter would look something like this. The DASL property tags aren't

URL's, they are actually the DASL equivalent of "MessageClass".

"http://schemas.microsoft.com/mapi/proptag/0x001a001e" LIKE 'IPM.Note%' OR

"http://schemas.microsoft.com/mapi/proptag/0x001a001e" LIKE 'IPM.Post%'

I'd construct that using StringBuilder myself probably:

StringBuilder sb = new StringBuilder();

sb.Append(@"http://schemas.microsoft.com/mapi/proptag/0x001a001e" + @" LIKE

'IPM.Note%' OR" + @"http://schemas.microsoft.com/mapi/proptag/0x001a001e" +

@" LIKE 'IPM.Post%'");

string filter = "@SQL=" + sb.ToString();

Microsoft.Office.Interop.Outlook.Items oTestItems =

oFldr.Items.Restrict(filter);

"Emrak" <Emrak> wrote in message

news:5DC7B176-4168-4A02-ADE6-C26B220D19CC@microsoft.com...
> I am making the assumption as of now (tell me if I'm wrong), that I can
> only
> process Posts and Notes separately. I thank you for your time.
 
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