SharePoint development is finally catching up with industry standards when it comes to implementing new functionality on your sites. Webhook is one of these standards that has been introduced in 2016 for SharePoint Online. It gives your organisation the ability to get notified when something happens in your list or library, but it involves a new way of processing these notifications. This session is for you if you want to learn to work with this newly introduced functionality like subscribing to a webhook, event processing, getting the latest changes, and more.

1. Getting notified by SharePoint with
the webHook functionality
Elio Struyf – Trainer @ U2U – MVP

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What are WebHooks?

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What are WebHooks?
• Event driven notifications AKA callbacks from the web
• Universal model used by many services: GitHub, Slack, MailChimp, …
• Pushing mechanism  asynchronous!
• Implemented in various Office 365 Services
• Microsoft Graph
• Connectors
• SharePoint

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WebHooks in SPO went GA
in January 2017

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Where can you use them?
• SharePoint
• List
• Libraries
• Microsoft Graph
• Messages, events, contacts, conversations in groups, OneDrive root items

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The good and the bad
• WebHooks are asynchronous mechanism
• Retry mechanism
• 5 times with a delay of 5 minutes
• More secure, no event information is passed
• No support for event-ing events  only RER can be used
• Add-ing, update-ing, delete-ing
• Requires some setup, but once done, it is easy to maintain

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Remote event receivers vs WebHooks
Remote event receivers
• Synchronous (-ing) and/or async (-ed)
• One request
• One change = one request
• Changes are inside the request body
• 2 minutes to respond
• Indefinitely
• One try
WebHooks
• Async only
• Retry logic: 5 times
• Batched requests
• Only notification  more secure
• 5 seconds to respond
• Needs subscription renewal
• When it fails, you can try again later
Both use the same base principle: call an external URI when something happens

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How to start using
WebHooks?

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By subscribing to a WebHook!
Notification service
1. Create a subscription
4. SharePoint responds with subscription info

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Important things about subscribing
Subscribing: POST - /_api/web/lists/getbytitle('Title')/subscriptions
{
"resource": "https://tenant.sharepoint.com/sites/site/_api/web/lists/getbytitle('Title')",
"notificationUrl": "Your notification service URL – HTTPS is required",
"expirationDateTime": "Date value - maximum 6 months",
"clientState": "String value for validation (optional)"
}

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Important things about subscribing
SharePoint calls your notification service:
POST - https://notification-service?validationToken={random-guid}
Respond with:
Important: notification service needs to respond in < 5 seconds
Status: 200
Body: validationtoken

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Important things about subscribing
When validation is done, SharePoint returns the subscription
information

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Local development and testing:
ngrok - Secure tunnels to localhost
https://ngrok.com/

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Demo
Subscribing to a WebHook

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More about the notification
service

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Notification service details
• You choose the technology: Web API, Node.js, …
• Respond in < 5 seconds and with status: 200-299 range
• Retry mechanism  5 times (5 minute in between)
• Not for the validation process
• Receives minimal information, just a message “something” happened
• Service has to gather the changes from SharePoint

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Minimal notification information?

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This is what you will receive
{
"value": [
{
"subscriptionId":"2e7f9cd7-5cdb-4d57-b4d5-edc083202378",
"clientState":null,
"expirationDateTime":"2017-08-16T10:38:54.3440000Z",
"resource":"465b36fc-e778-4047-8425-3f906497dfc3",
"tenantId":"9fee8694-d491-4e3e-b10b-a81ee76dfad9",
"siteUrl":"/sites/Webhooks",
"webId":"e363e4e9-0161-495f-a652-15c618e2e963“
}]
}

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How do I know what happened?
• SPList.GetChanges method
• POST - `/_api/web/lists(guid'${resource}')/getchanges`
• Specify a change query + change token
{
"Item": true,
"Add": true,
"Update": true,
"DeleteObject": true,
"Restore": true,
"ChangeTokenStart": {
"StringValue": "1;3;465b36fc-e778-4047-8425-3f906497dfc3;636307008298500000;60877869"
}
}
ChangeQuery properties: http://elst.es/2rib2q7

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Anatomy of the change token
1;3;465b36fc-e778-4047-8425-3f906497dfc3;636307008298500000;60877869
Version information (currently always 1)
Scope of the change. 3 = List & library changes.
Resource ID, can be retrieved from the subscription notification
Timestamp in ticks
Change number
in the event
cache table. You
can start with -1.

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Using the change token
• Using GetChanges without ChangeToken would return everything
• By specifying a change token, you control what you need

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Things to know about the change token
• First time, create it yourself (ex.: get all changes of the last hour)
• Per GetChanges request, you get the latest change token
• Store the latest change token, use it for the next call
{
"ChangeToken": {
"StringValue":"1;3;465b36fc-e778-4047-8425-3f906497dfc3;636307074435230000;60879219"
},
"ChangeType": 2,
"SiteId": "1432d309-9f6a-4dae-8d35-532dec332b86",
"ItemId": 3,
…
}

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GetChanges response value
• Notice the ChangeType, it is an enumeration
• 1 = added, 2 = updated, 3 = deleted
{
"ChangeToken": {
"StringValue":"1;3;465b36fc-e778-4047-8425-3f906497dfc3;636307074435230000;60879219"
},
"ChangeType": 2,
"SiteId": "1432d309-9f6a-4dae-8d35-532dec332b86",
"ItemId": 3,
"ServerRelativeUrl":"",
…
"WebId":"e363e4e9-0161-495f-a652-15c618e2e963"
}
More information about the ChangeTypes - http://elst.es/2ruAfKn

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Supported event types
• Added
• Updated
• Deleted
• CheckedOut
• CheckedIn
• UncheckedOut
• AttachmentAdded
• AttachmentDeleted
• FileMoved
• VersionDeleted
• FileConverted

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Creating your notification
service

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Tokens, all about the OAuth tokens
• Azure AD app registration
• Generate a certificate
• SharePoint requires access tokens with appidacr property set to 2
• Application Authentication Context Class Reference
• 0 = Public client
• 1 = Identified by a client id and secret
• 2 = Identified by a certificate

31. Azure AD application manifest
Store this in a separate file (privatekey.pem)
Fingerprint is also require to get the access token

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public getAppOnlyAccessToken(config: IConfig): Promise<any> {
return new Promise((resolve, reject) => {
const certificate = fs.readFileSync(path.join(__dirname, 'privatekey.pem'), { encoding : 'utf8'});
const authContext = new adal.AuthenticationContext(config.adalConfig.authority);
authContext.acquireTokenWithClientCertificate(config.adalConfig.resource, config.adalConfig.clientID, certificate,
config.adalConfig.fingerPrint, (err, tokenRes) => {
if (err) {
reject(err);
}
const accesstoken = tokenRes.accessToken;
resolve(accesstoken);
});
});
}
Get an access token via a certificate and
private key with ADAL for JS

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Important APIs
• Retrieve all list / library subscriptions
GET - /_api/web/lists/getbytitle('ListTitle')/subscriptions
• Update a subscription
PATCH - /_api/web/lists/getbytitle('ListTitle')/subscriptions('${subId}')
Body: { "expirationDateTime": "New expiration date" }
• Delete a subscription
DELETE - /_api/web/lists/getbytitle('ListTitle')/subscriptions('${subId}')

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Demo
Sample application

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A real life setup and configuration
SPO config page
HTTP Triggered function
Queue triggered function
1. Subscribe 2. Validate
3. Trigger change
4. Notify service
5. Put notification message on a queue6. Respond with 200
Use the page to:
- Check subscriptions
- Update subscriptions
- Delete subscriptions
7. Trigger another Azure function that will do change handling
8. Retrieve latest change token10. Store latest change token

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Demo
SPFx + Azure Functions

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Recap
• Notification service has to respond in < 5 seconds
• Retry mechanism  5 times (5 minute delay)
• Not for the validation process
• Subscription expiration date: 6 months
• Create a check or renewal process in your subscription processor
• You need to ask for the changes that happened  minimal
information is send
• Get the changes only what you are interested in
• No synchronous events for SPO  event-ing events

39. Questions?

40. Office Servers & Services MVP
Azure / Office 365 / SharePoint
@eliostruyf
www.eliostruyf.com
info@estruyf.be
Elio Struyf
Lead trainer and architect

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Resources
Certificate creation process with makecert - http://elst.es/2rhveZc
Keycred GitHub - http://elst.es/2pW77vm
All about the Change token - http://elst.es/2runG1M
ChangeType enumeration - http://elst.es/2ruAfKn
ChangeQuery properties - http://elst.es/2rib2q7
C# Sample application - http://elst.es/2qUYg0M
Node.js / TypeScript sample application - http://elst.es/2qVpTqT or http://elst.es/2cycM82
SharePoint List WebHooks docs - http://elst.es/2qwl1as - http://elst.es/2quVjD0