Lock a file from being accessed while it is in use by another process.

Hi,

How to lock a file from accessing while it is written by another process.
for eg:
I am creating a service which fetches the image from the video server and saves in a location for every 1 seconds,
the same is fetched from the saved location and displayed in an image control, so i get "Cannot access the file as it is being used by another process" error.
Can anyone help me how to prevent the file from accessing while it is being saved.
thanks,

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