Graph API Drive Items creating a folder under the root

Question

I'm using a lot of functions from msgraph. Now I stuck on creating a folder under the root.
This will give an invalid request. Already searched a lot sites, used copilot to get answer. But with no results.

 addedDriveItem = await graphClient
     .Drives[driveItemId]
     .Items["root"]
     .Children
     .PostAsync(driveItem);

var driveItem = new DriveItem
{
    Name = PrepareDriveItemName(dossierName).Trim(),
    Folder = new Microsoft.Graph.Models.Folder(),
    AdditionalData = new Dictionary<string, object>
    {
        { "@microsoft.graph.conflictBehavior", "fail" },
    },
};

Already tried this:

var requestInfo = graphClient
    .Drives[clientRootDriveId]
    .Items["root"]
    .Children
    .ToPostRequestInformation(driveItem);

addedDriveItem = await graphClient
    .RequestAdapter
    .SendAsync<DriveItem>(
        requestInfo,
        DriveItem.CreateFromDiscriminatorValue);

and

addedDriveItem = await graphClient
    .Drives[clientRootDriveId]
    .Items[driveItemId]
    .Children
    .PostAsync(driveItem);

Also looked at the application rights and I think I don't miss any.

Answer 1

To create a folder directly under the root of a drive with the Microsoft Graph SDK, the request must target the drive’s root item correctly. The invalid request comes from using Items["root"], which expects an item ID, not the literal string "root".

Use the Root navigation or the /root/children pattern instead of Items["root"].

For example, the REST call to create a folder in the signed-in user’s OneDrive root is:

POST https://graph.microsoft.com/v1.0/me/drive/root/children
Content-Type: application/json

{
  "name": "New Folder",
  "folder": { },
  "@microsoft.graph.conflictBehavior": "fail"
}

The equivalent SDK pattern is (conceptually):

var driveItem = new DriveItem
{
    Name = PrepareDriveItemName(dossierName).Trim(),
    Folder = new Microsoft.Graph.Models.Folder(),
    AdditionalData = new Dictionary<string, object>
    {
        { "@microsoft.graph.conflictBehavior", "fail" },
    },
};

// For the current user’s default drive root
var addedDriveItem = await graphClient
    .Me
    .Drive
    .Root
    .Children
    .PostAsync(driveItem);

// Or, for a specific drive by ID
var addedDriveItem2 = await graphClient
    .Drives[clientRootDriveId]
    .Root
    .Children
    .PostAsync(driveItem);

Key points:

1. Do not use Items["root"] when the SDK expects an item ID.
2. To create under root, use:
   • Me.Drive.Root.Children.PostAsync(...), or
   • Drives[drive-id].Root.Children.PostAsync(...).
3. Ensure the app has at least Files.ReadWrite (delegated) or Files.ReadWrite.All (application) permissions as documented for driveItem-post-children.

If creating under a subfolder instead of root, use the parent folder’s item-id:

var addedDriveItem = await graphClient
    .Drives[clientRootDriveId]
    .Items[parentItemId]
    .Children
    .PostAsync(driveItem);

This matches the documented POST /drives/{drive-id}/items/{parent-item-id}/children pattern.

---

References:

• Create a new folder in a drive
• List children of a driveItem
• Working with files in Microsoft Graph
• Get driveItem
• Move a driveItem to a new folder