Getting “Meeting Id is corrupted” error while trying to fetch meeting details from Graph API

It took me ages to reverse-engineer this, but I found a working solution.

Shame, shame, shame on Microsoft for working in silos and not attempting to fix the resulting mess.

In a nutshell, you need to do some replacing of the meeting id from the one you have from Teams into Graph.

The step-by-step process is as follows:

• The ID you get from Teams looks like "MCMxOTptZWV0aW5nX016YzJabVkzT0RFdFl6QTJaaTAwT1RBMExXRXlNRFF0T0RkbVl6TTRNRE15TlRJMkB0aHJlYWQudjIjMA=="
• You decode the Base64, leading to "0#19:meeting_Mzc2ZmY3ODEtYzA2Zi00OTA0LWEyMDQtODdmYzM4MDMyNTI2@thread.v2#0"
• You then need to get rid of "0#" and "#0", hence "19:meeting_Mzc2ZmY3ODEtYzA2Zi00OTA0LWEyMDQtODdmYzM4MDMyNTI2@thread.v2"
• The prepend "1*" + <GUID of the User> + "*0**", resulting in "1*b2267176-534c-4bef-800a-d598623e2f7f*0**19:meeting_Mzc2ZmY3ODEtYzA2Zi00OTA0LWEyMDQtODdmYzM4MDMyNTI2@thread.v2"
• Finally, Base64 the result "MSpiMjI2NzE3Ni01MzRjLTRiZWYtODAwYS1kNTk4NjIzZTJmN2YqMCoqMTk6bWVldGluZ19NemMyWm1ZM09ERXRZekEyWmkwME9UQTBMV0V5TURRdE9EZG1Zek00TURNeU5USTJAdGhyZWFkLnYy"

Here is a complete implementation in C# from ITurnContext. I have two extensions methods to convert to and from Base64, which I'm not herein including:

 public static async Task<IReadOnlyList<SimpleChatMessage>> GetTranscript(ITurnContext turnContext, CancellationToken cancellationToken = default)
 {
         var participants = await TeamsInfo.GetMembersAsync(turnContext);
         var firstPartipant = participants.First();

         var meetingId = System.Text.Encoding.UTF8.GetString(channelData.Meeting.Id.FromBase64String());

         var meetingLongId = "1*" + firstPartipant.AadObjectId + "*0**" + meetingId.Replace("#0", "").Replace("0#", "");
         meetingLongId = meetingLongId.ToBytes().ToBase64String();

             var currentPage = await GraphServiceClient.Users[firstPartipant.AadObjectId].OnlineMeetings[meetingLongId].Transcripts.GetAsync(requestConfiguration =>
             {
                 // requestConfiguration.QueryParameters.Top = 1; // maximum
                 //requestConfiguration.QueryParameters.Orderby = new string[] { "createdDateTime desc" };
             }, cancellationToken).ConfigureAwait(false);

             var latestTranscript = currentPage.Value.Last();
         }