SharePoint 2013 - GroupUserAdded event receiver not firing when adding user programmatically to group

Question

I've added a GroupUserAdded event receiver to a SPWeb and confirmed the correct deployment via SharePoint Manager.

Additionally, the call to the receiver class is working fine when adding a user via SP Site Settings page People and Groups.

The caveat I'm experiencing right now - and couldn't find a fix for - is that programmatically adding a user to a group as follows won't trigger the event receiver. Any idea as though why this behaviour occurs would be appreciated.

var firstGroup = web.SiteGroups[0];
var adminUser = web.EnsureUser("administrator");
firstGroup.AddUser(adminUser);
firstGroup.Update();

ty, Frank

Answer 1

Try adding System.Threading.Thread.Sleep(1000); after the Update. Sometimes async events are not triggering properly.

Similar case but with item event receiver: Programmatically changing a field won't trigger the event receiver