how do i read a file open in another program?

I'm trying to read from a *txt file that a program uses as a log.  I haven't found any good articles on reading from logs using C#. so i created a streamreader object and i have it read from the log.txt

well, i want to read from the log while it's being updated by another program, so i have a file systemwatcher that triggers a change event, and that event tells the streamreader to go look at the file.  but I keep getting an error from the streamreader that it can't access the file since it is open by another program. 

what am i doing wrong? is the streamreader the wrong object to use?