Fixing "Identifier Malformed" and "Resource Not Found" Errors When Uploading to SharePoint with C# and MS Graph SDK

Uploading files to SharePoint using Microsoft Graph in C# can be tricky, especially when dealing with site paths and drives. Let’s break down why you’re seeing errors like Provided identifier is malformed or Resource not found for the segment 'Documents' and how to resolve them.

Understanding the Problem

Your code tries to access a SharePoint site and its drive like this:

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var driveItem = await client.Sites["acme.sharepoint.com/sites/ndexport1"].Drive.GetAsync();  

This fails because the site identifier format is incorrect. Similarly, trying to include Documents in the path (e.g., .../ndexport1/Documents/) throws a Resource not found error because Documents is a drive, not a site segment.

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Step 1: Correct the Site Identifier

The Microsoft Graph API expects site identifiers in a specific format:

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// Use colon (:) and slash (/) to specify the server-relative path  
var site = await client.Sites["acme.sharepoint.com:/sites/ndexport1"].GetAsync();  

• Why This Works: The :/ syntax tells Graph to treat the path as relative to the SharePoint tenant root.

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Step 2: Access the Drive (Document Library)

Once you have the correct site reference, retrieve its default drive (e.g., the Documents library):

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var drive = await client.Sites["acme.sharepoint.com:/sites/ndexport1"].Drive.GetAsync();  

• No Need for /Documents: The Drive property points to the default document library.

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Step 3: Upload Files to the Drive

Use the drive ID to upload files:

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// Example: Upload to the root folder of the drive  
var uploadSession = await client.Drives[drive.Id].Root  
    .ItemWithPath("myfile.txt")  
    .CreateUploadSession()  
    .Request()  
    .PostAsync();  

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Why Your Original Code Failed

1. Malformed Identifier:

   • ❌ client.Sites["acme.sharepoint.com/sites/ndexport1"]

   • ✅ client.Sites["acme.sharepoint.com:/sites/ndexport1"]

   • Missing : and / caused the malformed error.

2. Invalid Path for Documents:

   • The Documents library is a drive, not part of the site path.

   • Use Drive after resolving the site correctly.

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Full Working Example

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using Microsoft.Graph;  
using Azure.Identity;  

var scopes = new[] { "https://graph.microsoft.com/.default" };  
var options = new ClientSecretCredentialOptions { AuthorityHost = AzureAuthorityHosts.AzurePublicCloud };  

var authProvider = new ClientSecretCredential(_tenantId, _clientId, _clientSecret, options);  
var client = new GraphServiceClient(authProvider, scopes);  

// 1. Get the site with the correct identifier  
var site = await client.Sites["acme.sharepoint.com:/sites/ndexport1"].GetAsync();  

// 2. Get the drive (document library)  
var drive = await client.Sites[site.Id].Drive.GetAsync();  

// 3. Upload a file  
using var fileStream = File.OpenRead("path/to/yourfile.txt");  
var uploadSession = await client.Drives[drive.Id].Root  
    .ItemWithPath("yourfile.txt")  
    .CreateUploadSession()  
    .Request()  
    .PostAsync();  

var uploadTask = new LargeFileUploadTask<DriveItem>(uploadSession, fileStream);  
var result = await uploadTask.UploadAsync();  

if (result.UploadSucceeded)  
    Console.WriteLine("File uploaded!");  

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Alternative: Use Site ID or Drive ID

If you know the Site ID or Drive ID, use them directly:

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// By Site ID  
var site = await client.Sites["{SITE_ID}"].GetAsync();  

// By Drive ID  
var drive = await client.Drives["{DRIVE_ID}"].GetAsync();  

• Find these IDs in the SharePoint URL or via the Graph API.

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Key Takeaways

1. Use :/ in site identifiers for server-relative paths.

2. Access drives through the Drive property of a site.

3. Avoid adding Documents to the site path—it’s a drive, not a segment.

With these fixes, you’ll bypass malformed identifier errors and upload files successfully! 🚀