how to save the compose message text in draft automatically?

we have a vb.net application with send and receive mailing also. Now we have added a session timer of 30 min but the users are complaining that they are facing a problem when they write a long text message or while composing they get busy in something else and when they return back to continue composing message , they are redirected to a ses开发者_如何学Gosion expiry page, and their long text message is gone forever. So I am new to this and I was thinking like , when the user is in compose message the text should be automatically saved to drafts like hotmail. Any help will be appreciated . Thank you.

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There are two basic approaches you can take to this:

1. The proper "web" way would be to remove the need for session and state from at least this part of the application i.e. set up the application so that its resilient if the session expires and can pick up the necessary user details etc from the post if the session has expired - you can do this with a value stored in viewstate or in a cookie. However this doesn't deal with the problem of saving work in progress.
2. So the more appropriate solution here will be to investigate AJAX solutions to the problem whereby the page uses client side scripting to transparently "save" (post) the message text back to the server at defined intervals. This has the further advantage of prolonging the session as well.

Of course with the AJAX solution your back end data management becomes more complex too... but it that's manageable (limit it to one draft in progress and remember to clear out the draft on "send" and you should be fine) and you may still want to consider some degree of additional resiliency for loss of session for other reasons.