Waits for the task to finish.
For properly ending a task, the
Finish method (see below) must be called. The task result object and exception information can be obtained then. When Wait returns
true, calling the
Finish method will not block; it will otherwise.
Has the task finished?
If this property returns
Finish method will not block when called.
Special TinmanError object that is used when a task has been cancelled by the user.