My GraphEmailClient method for retrieving pages of messages from a specific folder looks like this:

        {
            //this is because the ids sometimes end with equals signs, which get truncated in a querystring
            MailFolderId = MailFolderId.TrimEnd('ÿ').TrimStart('ÿ');
            IMailFolderMessagesCollectionPage pagedMessages;

            try
            {
                if (nextPageLink == null)
                {
                    // Get initial page of messages
                    pagedMessages = await _graphServiceClient.Me.MailFolders[MailFolderId].Messages
                            .Request()
                            .Select(msg => new
                            {
                                msg.Subject,
                                msg.BodyPreview,
                                msg.ReceivedDateTime,
                                msg.From,
                                msg.IsRead,
                                msg.HasAttachments
                            })
                            .Top(top)
                            .OrderBy("receivedDateTime desc")
                            .GetAsync();
                }
                else
                {
                    // Use the next page request URI value to get the page of messages
                    var messagesCollectionRequest = new MailFolderMessagesCollectionRequest(nextPageLink, _graphServiceClient, null);
                    pagedMessages = await messagesCollectionRequest.GetAsync();
                }
            }
            catch (Exception ex)
            {
                _logger.LogError($"Error calling Graph /me/messages to page messages: {ex.Message}");
                throw;
            }

            return (Messages: pagedMessages,
                    NextLink: GetNextLink(pagedMessages));
        }

The OnGetAsync routine in my codebehind looks like this:

        public async Task OnGetAsync(string mailfolder)
        {
            var messagesPagingData = await _graphEmailClient.GetMailFolderMessagesPage(mailfolder, NextLink);
            FolderId = mailfolder;
            Messages = messagesPagingData.Messages;
            NextLink = messagesPagingData.NextLink;
            await Task.CompletedTask;
        }

And finally, my Next button in the Razor page looks like this:

            @if (!String.IsNullOrEmpty(Model.NextLink)) {
                <a asp-page="/EmailPreview?mailfolder=@fixedfolder&[email protected]" asp-route-nextlink="@Model.NextLink" class="btn btn-primary" style="width:270px">Next Page</a>
            }

When I omit the querystrings on the asp-page, the NextLink value comes through correctly, because of the asp-route-nextlink. But the folderid does not. It shows up as null, even if I put this on the page:

<input type="hidden" name="folderid" id="folderid" value="@Model.FolderId" />

Which is why I got rid of that line and added folderid into the asp-page address. But that stopped NextLink from coming through. I seem to be able to get one or the other, but not both.

All of this works fine if I use IUserMessagesCollectionPage instead of IMailFolderMessagesCollectionPage, and do everything without specifying a mail folder. But I need to specify a folder, so that doesn’t help me.