Creating Outlook Application Object reference not set to an instance of an object

Question

Hello I am creating a new Outlook.Application (with v.14.0.0.0 Office library) and retrieving the inbox email with C#. Only when outlook is not running, I am getting the error

'Object reference not set to an instance of an object'

in a alert(Occurred by the first line). The program is runnig ahead(doesn't even go in the catch part).

try {
    Outlook.Application outlookApplication = new Outlook.Application();
    Outlook.NameSpace mapiNameSpace = outlookApplication.GetNamespace("MAPI");
    Outlook.MAPIFolder folder = mapiNameSpace.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderInbox);

    foreach (Object obj in folder.Items) {
        if (obj is Outlook.MailItem) {
            Outlook.MailItem mailItem = (Outlook.MailItem)obj;
        }
    }
} catch (Exception e) {
    Console.WriteLine("Unfortunately an error occurred");
    Console.WriteLine(e.Message);
}

Is there any solution for this annoying alert? Can I suppress it or fix the problem?

The alert is coming from a Outlook instance, I can see it because in the navigation bar a outlook instance is open (the little alert dialog).

Solution

You'll need to first try and get a reference to the running instance, and only create a new one (new Outlook.Application()) if an existing instance can't be attached to.

This MSDN article makes it pretty clear.

Shameless rip directly from MSDN article:

Outlook.Application application = null;

// Check whether there is an Outlook process running.
if (Process.GetProcessesByName("OUTLOOK").Count() > 0)
{

    // If so, use the GetActiveObject method to obtain the process and cast it to an Application object.
    application = Marshal.GetActiveObject("Outlook.Application") as Outlook.Application;
}
else
{

    // If not, create a new instance of Outlook and log on to the default profile.
    application = new Outlook.Application();
    Outlook.NameSpace nameSpace = application.GetNamespace("MAPI");
    nameSpace.Logon("", "", Missing.Value, Missing.Value);
    nameSpace = null;
}