Update item data (patch) but nothing happens

[nepgya2803]

I'm new to pnp core. My goal is to update the item data (user data), after going through many documents, threads and discussion, here is what I got. Even though the debug console show that a patch request was sent, but the item still hasn't been changed

public async Task Update(PnPContext context)
        {
            var myList = await context.Web.Lists.GetByTitleAsync("My list");

            string viewXml = CAMLQueryGenerator("5106686");

            await myList.LoadListDataAsStreamAsync(new RenderListDataOptions()
            {
                ViewXml = viewXml,
                RenderOptions = RenderListDataOptionsFlags.ListData
            });

            foreach (var item in myList.Items)
            {
                // Here if the employee number is equal to the one need to be updated, it will do the update and stop
                if (item["EmployeeNumber"].ToString() == "5106686")
                {
                    item["Specialty"] = "xxxxxx";
                    await myList.UpdateAsync();
                    break;
                }
            }
        }

And here is my calm query

private string CAMLQueryGenerator(string employeeID)
        {
            string caml = "<Query>" +
                    "<Where>" +
                      "<Eq>" +
                          "<FieldRef Name='EmployeeNumber'/>" +
                          "<Value Type='Text'>" + employeeID + "</Value>" +
                      "</Eq>" +
                      "</Where>" +
                    "</Query>";

            return caml;
        }

[jansenbe]

@ngqtrieu99 : that code should work although please fix the following by adding an .AsRequested() here:

...
foreach (var item in myList.Items.AsRequested())
...

If that's not working check the payload of the patch request to ensure the field in included. Alternatively try the UpdateOverwriteVersionAsync (see https://pnp.github.io/pnpcore/using-the-sdk/listitems-intro.html#updating-list-items) method

[nepgya2803]

It really works. Changing into AsRequested() and using UpdateOverwriteVersionAsync () really did the job. Can you explain why we need them?

[jansenbe]

@ngqtrieu99 : using the LoadListDataAsStreamAsync you already loaded the items in the collection, when you want to iterate over the loaded items you need to add .AsRequested() as otherwise our LINQ provider thinks you want to perform a new query. The UpdateOverwriteVersionAsync uses another update model, but still that shouldn't be required. You can use Fiddler to check what goes over the wire