Believe, I almost went FXXXX CRAZY trying to get this working on a recent project.

Microsoft Graph

I like the idea behind Graph (really, we use it in our projects and works fairly good although some features still need some elbow grease from the dev-team.).

Having a centralized entrypoint to the “suite” of Microsoft services that’s REST oriented, with a good SDK (.NET Core in this case) and with somewhat of a fluent-API model (memberOf stil doesn’t work for users…DUH) is great and provides easy integration for apps but some features can be a bit confusing or “tricky” to get working.

This may be one of those things that when you already know it seems stupid simple but believe me…I wasted almost two days to get it working

Subscriptions are the new webhooks

Wanting to create a new Sharepoint Webhook so you get notified when a new Avril Lavigne gif gets uploaded?

Way 1…do a wrapper over the Sharepoint api or just hardCode the Http call and call it a day.

Way 2…have some intern running around yelling that a new file has been uploaded, but HR may not like that.

Way 3…use the Graph API you already have integrated into your project to avoid coupling to yet-another-external-service.

3 looks good? Welcome to the world of suscriptions and drives.

Creating a Graph subscription

Graph subscription objects are designed to work over a wide range of resources and services so we need them to “configure” them a bit.

The main fields of a subscription creation are:

• ChangeType => What changes are going to trigger the subscription (updated,created,deleted)
• NotificationUrl => Really, I need to explain this one?
• Resource => What resource is going to be monitored for changes
• ExpirationDateTime => Subscription lifetime, this changes from resource to resource but usually is something between 30 and 180 days.

When accessing Sharepoint resources over Graph everything is considered as a “Drive” or “DriveItem” (hi there, OneDrive for Business) so we have some constraints over what we can do.

First of all, you can only set a subscription over the root of a sharepoint library so the subscription will trigger for every change in any underlying item or folder.

Because of this, only the ChangeType “updated” is valid.

(you need to know the driveId of the sharepoint library that you want to monitor…graphExplorer is very useful for this)

And aaaaaaalso, the max ExpirationDateTime is one month from the subscription creation date. You need to implement your own refresh/renewal service.

Example of a valid Subscription model in C#:

var subscription = new Subscription
{
    ChangeType = "updated",
    NotificationUrl = notificationUrl,
    Resource = $"drives/{driveId}/root",
    ExpirationDateTime = DateTime.UtcNow.AddDays(30)

};
result = await this.graphStableClient.Subscriptions.Request().AddAsync(subscription);