How can I "undo send" like in Gmail?

How can I undo send, save or delete in Vb like Gmail is using this feature in Messages. The feature used by Gmail is they are queing the message for 5 secs and if the user clicks on Undo before that 5secs the whole send process is pulled back.

Now what I want is to implement this same in my Vb.net application. Is there any code available to do this. Please help ?

Solution

About an "undo send" feature, the most evident way of doing that is to actually not "do" what you want to "undo".

What I mean is :

When a user clicks on "send", you should not really send the message
Instead, you should mark it as "to send in X seconds" -- place it in some queue, for instance
Which means it'll only be sent after X seconds, and not immediatly.
During this X number of seconds, if the user clicks "undo send", you just have to remove that mail from the "waiting queue"

Of course, you cannot "undo send" on a mail which has already been sent : it's gone from your server, and there is nothing you can do anymore about it.

To implement that, you'll need :

Some queue for actions
To place your data into this queue when the user clicks "send"
To have some batch that really sends data that's been in the queue for more than X seconds
To remove the data from the queue when the user clicks "undo send".

The same idea can be applied to "undo delete" :

When a user clicks on "delete", don't physicilly delete the data
Instead, use some boolean flag to indicate that it should be considered as deleted
Then, un-doping that deletion only means de-activating that flag

This can easily be implemented in any language :

Add a is_deleted field on your data
When displaying the data, filter those for which this flag is enabled
When deleting, instead of physically deleting, set this flag
When un-deleting, un-set this flag

The "undo save" can be a bit harder : a solution would be to not keep only one version of the message, but several :

Each time the user clicks "save", you should store a new version of the message
Which means you'll end up, after some time, with many versions of the message
Which will allow you to "come back" to a previous version, restoring it from the history.

This can be done :

adding a new field called like "version" on your data.
each time the user saves, just increment that field, and store a copy of the data
i.e. never actually update any exiting data, but always insert a new version of it.
then, "undo save" only means "get the previous version of the data"