In Graph API, attachments are tied to a specific message. You need the UserId (or email address), the MessageId , and the AttachmentId . Step A: List Attachments First, you typically need to find the attachment ID.
For fileAttachment types, you must access the $value endpoint to get the raw byte stream. microsoft graph api download attachment c#
Message IDs often contain slashes or special characters. The SDK handles URL encoding for you, but be careful if you are building strings manually. In Graph API, attachments are tied to a specific message
Always check if an attachment is a FileAttachment before trying to download content. ItemAttachment (emails) and ReferenceAttachment (cloud links) require different handling. 6. Quick Check: Is it a File? For fileAttachment types, you must access the $value
var attachment = await graphClient.Users[userId] .Messages[messageId] .Attachments[attachmentId] .GetAsync(); if (attachment is FileAttachment fileAttachment) { // Proceed with download Console.WriteLine($"Downloading: {fileAttachment.Name}"); } Use code with caution.