https://learn.microsoft.com/en-us/dotnet/api/microsoft.rtc.collaboration.call.endsendmessage?view=ucma-api
Call.EndSendMessage(IAsyncResult) Method (Microsoft.Rtc.Collaboration) | Microsoft Learn
This method is used to determine whether the corresponding operation completed successfully. This method will wait if the operation has not yet completed
callmethodmicrosoftrtccollaboration