ClientContext API will not return items in Teams SharePoint site, works fine in SharePoint Online

Question

Would there be a difference in using the 'older' SharePoint ClientContext/CSOM based API against a site in SharePoint Online versus one that is a part of a Team?

I have a bit of code that works just fine when talking to a general SPO site.

using (var cc = new AuthenticationManager().GetACSAppOnlyContext(instance.url, instance.apiKey, instance.apiSecret))
{    
    Web web = cc.Web;
    var spTimezone = web.RegionalSettings.TimeZone;

    List eventsList = web.Lists.GetByTitle(instance.calendarTitle);
    CamlQuery query = CamlQuery.CreateAllItemsQuery(); 
    var list = web.Lists;

    ListItemCollection eventsItems = eventsList.GetItems(query);
    cc.Load(eventsItems);
    cc.ExecuteQuery();

    Logger.Info("Found " + eventsItems.Count + " items in " + instance.name);
}

But, if I run this against a site I am working on now, I get zero results. If I run against several sites I developed this code against (not tied to a Team) it works as expected and returns me a collection of list items.

I feel that my auth is working, as if I spell CalendarTitle wrong, I get an exception that List does not exist at URL.

I also can not seem to be able to see a list of all lists in the site, etc.

Is this due to a difference in this particular site? Why would I not be able to get any results, when it works fine on all of my other, non-Teams based sites?

Answer 1

Whether we're talking about C# or PowerShell, we need to authenticate in order to interact with SharePoint Online.

Right now, Azure Control Service (ACS) is still available but it is deprecated and scheduled for retirement. It should function until April 2nd, 2026, or until it is explicitely disabled via PowerShell Command. More on ACS here.

To connect to SharePoint Online via ACS I suggest this article,

https://www.c-sharpcorner.com/article/connect-to-sharepoint-online-site-with-app-only-authentication/

Since ACS is old news, you may want to switch to the new Azure AD App.

The process is not easy but it is well documented in this article where Microsoft describes the step-by-step process of switching from ACS to Azure AD App,

https://learn.microsoft.com/en-us/sharepoint/dev/sp-add-ins-modernize/from-acs-to-aad-apps

There's a lot of misconceptions around CSOM but for now it's still alive and kicking with no end in sight as you can see here.

That said, if what you're trying to accomplish doesn't need to be done via C#, you can switch to PowerShell and connect via PnP PowerShell, which sort of works as its own app, where you connect interactively and run your scripts, just like in C# but in a PowerShell script, no app needed. You'll obviously need access rights to the site and the ability to run custom scripts. PnP supports many authentication methods, including ACS and Azure AD Apps, but you can connect without them if you have access and are ok with the interactive prompt.

Example:

Install-Package -Name PnP.PowerShell
connect-pnponline -url https://contoso.com -interactive
$events = Get-PnPListItem -list Events

More details here,

https://www.sharepointdiary.com/2019/07/how-to-run-powershell-scripts-for-sharepoint-online.html

PowerShell PnP Module,

https://github.com/pnp/powershell

Other notes

• Different PowerShell modules connect using a different context (Microsoft.Online.SharePoint.PowerShell connects you as an admin, PnP.PowerShell uses whatever credentials your provide, which can be your own)
• Make sure the account or credential that you use to connect actually has access rights to the resources, otherwise you'll keep getting issues where the connection works but the data is not returned
• Interestingly enough, you can use the PowerShell "app" to connect to a SharePoint site interactively via C# using the code below
• The "right" way to authenticate to SharePoint Online going forward is probably the creation of the Azure AD App, so you should give it a try if it's an option for you. You may need an admin to help with consenting the rights if you're not one yourself

.

var authManager = PnP.Framework.AuthenticationManager.CreateWithInteractiveLogin("31359c7f-bd7e-475c-86db-fdb8c937548e");
ctx = authManager.GetContext(url);