Upload user files

  • 3 minutes

In the next exercise, you'll extend the app to support file uploads. There are two ways to upload a file using Microsoft Graph. The easiest way is to use a single PUT request:

var driveItem = await _graphServiceClient
    .Me.Drive.Root
    .ItemWithPath(itemPath)
    .Content
    .Request()
    .PutAsync<DriveItem>(stream);

However, this method is limited to 4 MB. The more complex method involves a series of HTTP requests as an “upload session”. Fortunately, the Microsoft Graph SDK makes the complex method more straightforward! The aptly named LargeFileUploadTask object handles all the details.

To use LargeFileUploadTask object, an upload session must first be created:

var uploadSession = await _graphServiceClient.Me.Drive.Root
    .ItemWithPath(itemPath)
    .CreateUploadSession(uploadProps)
    .Request()
    .PostAsync();

The upload session is passed into the LargeFileUploadTask constructor along with the stream to upload and maximum slice size. The maximum slice size value must be a multiple of 320 KB:

int maxSliceSize = 320 * 1024;
var fileUploadTask = new LargeFileUploadTask<DriveItem>(uploadSession, stream, maxSliceSize);

To track the file upload progress, a Progress object can be created and passed into the LargeFileUploadTask object's UploadAsync method.

IProgress<long> progress = new Progress<long>(prog =>
{
  _logger.LogInformation($"Uploaded {prog} bytes of {stream.Length} bytes");
});

var uploadResult = await fileUploadTask.UploadAsync(progress);

To start the file upload, an HTML form can be added into the webpage with a file input and button:

<form method="post" enctype="multipart/form-data">
  <input asp-for="UploadedFile" type="file"></input>
  <input type="submit" value="Upload File"></input>
</form>

When a user submits a file upload, the data is assigned to a property named UploadedFile in the Razor Page model named FilesModel. The property's name matches the asp-for value defined in the form's file input control.

[BindProperty]
public IFormFile UploadedFile { get; set; }

Let's look at how these different parts can be put together to support file uploads.