如果文件大小介于3 MB和150 MB之间，请创建一个上载会话，并反复使用PUT上载文件的字节范围，直到上载完整个文件。最终成功的PUT响应中的标头包含一个带有附件ID的URL。

• • 样品：**

GraphServiceClient graphClient = new GraphServiceClient( authProvider );

var attachmentItem = new AttachmentItem
{
    AttachmentType = AttachmentType.File,
    Name = "flower",
    Size = {fileSizeInBytes}
};

await graphClient.Me.Messages["{message-id}"].Attachments
    .CreateUploadSession(attachmentItem)
    .Request()
    .PutAsync();

See the doc for more info - https://learn.microsoft.com/en-us/graph/outlook-large-attachments?tabs=csharp#step-1-create-an-upload-session