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

When I am a casting below code then i got an error

Code :

string subject = ((Microsoft.Office.Interop.Outlook.MailItem)myInbox.Items[temp])
    .Subject.ToString();

Unable to cast COM object of type 'System.__ComObject' to interface type 'Microsoft.Office.Interop.Outlook.MailItem'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{00063034-0000-0000-C000-000000000046}' failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).

You need to check the item type first. Outlook folders may contain various types of items:

Object selObject = this.Application.ActiveExplorer().Selection[1];
        if (selObject is Outlook.MailItem)
        {
            Outlook.MailItem mailItem =
                (selObject as Outlook.MailItem);
            itemMessage = "The item is an e-mail message." +
                " The subject is " + mailItem.Subject + ".";
            mailItem.Display(false);
        }
        else if (selObject is Outlook.ContactItem)
        {
            Outlook.ContactItem contactItem =
                (selObject as Outlook.ContactItem);
            itemMessage = "The item is a contact." +
                " The full name is " + contactItem.Subject + ".";
            contactItem.Display(false);
        }
        else if (selObject is Outlook.AppointmentItem)
        {
            Outlook.AppointmentItem apptItem =
                (selObject as Outlook.AppointmentItem);
            itemMessage = "The item is an appointment." +
                " The subject is " + apptItem.Subject + ".";
        }
        else if (selObject is Outlook.TaskItem)
        {
            Outlook.TaskItem taskItem =
                (selObject as Outlook.TaskItem);
            itemMessage = "The item is a task. The body is "
                + taskItem.Body + ".";
        }
        else if (selObject is Outlook.MeetingItem)
        {
            Outlook.MeetingItem meetingItem =
                (selObject as Outlook.MeetingItem);
            itemMessage = "The item is a meeting item. " +
                 "The subject is " + meetingItem.Subject + ".";
        }

See How to: Programmatically Determine the Current Outlook Item for more information.