Comments by obarahmeh (Top 1 by date)

There is an error for your sentences:
TaskItem OutlookTask = (TaskItem)Application.CreateItem(OlItemType.olTaskItem);
Application is an ambiguous between Outlook.Application and Window.forms.Application .

and the second sentence:
TaskItem OutlookTask = tasks.Items.add(OlItemType.olTaskItem);
shows an error in tasks which does not exist in this context

Is there any missing, any references??

I've referenced the following:
using Microsoft.Office.Core;
using Microsoft.Office.Interop.Outlook;