Task Command Pattern is used with a notification observer like pattern

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C#

Task

I am looking for a good way to implement a Task System with a Notification System.
If anyone is aware of any good resources I can look at for handling and combining both patterns.
I am sorry in advance, I do not have any sample code, but once I have a good idea how implement I will post some code.

I have three interface:
IProgram
Attach();
Detatch();
Notify();

ITask
Execute();

INotify
Update();

one Event:
NotifyEventArgs

Classes:
Notifier
Update()
obserState

AbstractTask
NotifyEvent
Execute();

TypesOfTask

FileProgram
GetState()
SetState()
subjectState