In umbraco 9+ you would create a notification handler for this.

Read up on how notifications work here https://docs.umbraco.com/umbraco-cms/reference/notifications

The notification you need to handle is https://docs.umbraco.com/umbraco-cms/reference/notifications/contentservice-notifications#saving

This will allow you to check if the content you are saving may contain the property that you want to handle.

public void Handle(ContentSavingNotification notification)
{
    foreach (var entity in notification.SavedEntities)
    {
        // if entity is the right type
        var blocks = [GetBlocksFromEntity];
        foreach(var block in blocks.Where(x => [BlockNeedsADate](x))
        {
            // set date
        }
    }
}

You would need to implement the two methods with [...]

Would this be the same way for V8? or is this even possible for v8?

Thanks Soren.

Yeah - the part of figuring out if a block item is 'dirty' is what I cannot figure out.

If I do add a datetime field, I don't think there is a way to figure out when that single block has been updated (and not the other blocks) - as far as my research has gone. If the content node is saved, then you would essentially be blanket updating the datetime field for all the blocks on that node and not just the ones that have been updated, which is not what I am looking for.

The key would be to determine if the block item is dirty. As far as I know, there is no history for blocks, such that we can do a compare with to see if it has changed.

Thanks Menno for your input.

You should be able to get the DateTime value from the block item and check it against: DateTime.MinValue. If the person creating the block item forgets to fill the property of the block item then the default value of the field will be DateTime.MinValue. Since you can hook into the saving event you can check if that value isn't DateTime.MinValue and if it is change that value to DateTime.Now. That way every block item will have a filled DateTime property. This doesn't work for edited block items of course. For those items you'd be depending on the editor to fill the right DateTime.

Yeah - i'm trying to avoid having the editor updating any sort of datetime manually. It should all be done programmatically and updated each time there is an update to the block item.

I want that datetime field to get populated/updated on save automatically as to not rely on the editor for this change.

This should be the case for both new and edited blocks.