Outlook Add-in Exception - How to check the type of Outlook.Item?

Question

I have an Outlook 2013 Add-in,

Outlook.MAPIFolder inboxFolder;
Outlook.Items mailInboxItems;

private void ThisAddIn_Startup(object sender, EventArgs e)
{
   ... other code ---

   mailInboxItems = inboxFolder.Items;
   mailInboxItems.ItemAdd += mailInboxItems_ItemAdd;
}

private void mailInboxItems_ItemAdd(object item)
{
   Outlook.MailItem emailMessage = (Outlook.MailItem)item; // cast error
   ProcessEmail(emailMessage);
}

An exception is thrown when, of course, the item coming in is not of type Outlook.MailItem:

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

How can I check that the parameter "item" is of only a valid type, i.e. Outlook.MailItem to avoid any exceptions?

Answer 1

You can use the "is" and "as" operators in C#. See How to: Programmatically Determine the Current Outlook Item for more information.

Also the Outlook object model provides the MessageClass property - a string representing the message class for the Outlook item. Under the hood the message class is used to identify what inspector to use in Outlook for displaying the item.