Validating document approval and sending email notification

Today I was working on a requirement to validate document approval (we are using OOTB document approval feature) based of some external business rules.

Requirement:

If business validation fails, I have to cancel document Approval process and if validation succeeds then I have to generate email notifying team with links to approved document.

Solution:

My first option was to use Workflow using Visual Studio (I have to re-use the functionality for many other document libraries), but soon found out it's not possible to retrieve before and after values inside Workflow and to cancel list item update. Please let me know if you think otherwise. The other option was to use Event Receiver which I followed. I override synchronous ItemUpdating event and again struggled to retrieve after "Approval Status" value. After couple of hours of debugging, I found key named vti_doclibmodstat in AfterProperites collection containing integer values 0, 1 or 2 which is nothing but Approved, Rejected or Pending statuses. So here is the complete code to retrieve before and after "Approval Status" inside event handler:

public override void ItemUpdating(SPItemEventProperties properties)
{
base.ItemUpdating(properties);

SPModerationStatusType beforeStatus = properties.ListItem.ModerationInformation.Status;

SPModerationStatusType afterStatus = 
(SPModerationStatusType)Int32.Parse(properties.AfterProperties["vti_doclibmodstat"].ToString());

if ((beforeStatus != afterStatus) && 
(afterStatus == SPModerationStatusType.Approved))

{

if (Validate(properties) == false)

{

properties.Cancel = true;

properties.ErrorMessage = "";

}

else

{

SendEmail(properties);

}

}

}

And now I can validate document approval process, cancel approval process and send email notifications.

Hope this helps.
-Javed