(401) Unauthorized exception while downloading file from SharePoint

Question

I have generated an access token using OAuth mechanism for SharePoint Online server. I am using this token to create ClientContext using CSOM. While I am able to access all the sites, libraries, and folders seamlessly, I get error

The remote server returned an error: (401) Unauthorized.

while downloading the file from SharePoint Online. Below is the code that I am using for file download:

    var clientContext = TokenHelper.GetClientContextWithAccessToken("https://adventurer.sharepoint.com/Subsite1", accessToken);
    var list = clientContext.Web.Lists.GetByTitle("SubSite 1 Library 1");
    string vquery = @"<View Scope='RecursiveAll'><Query><Where><Eq><FieldRef Name='UniqueId' /><Value Type='Lookup'>" + "6718053d-a785-489c-877f-5a4b88dcb2a7" + "</Value></Eq></Where></Query></View>";
    CamlQuery query = new CamlQuery();
    query.ViewXml = vquery;
    var listItems = list.GetItems(query);
    clientContext.Load(listItems, items => items.Take(1).Include(item => item.File));
    clientContext.ExecuteQuery();

    var fileRef = listItems[0].File.ServerRelativeUrl;
    var fileInfo = Microsoft.SharePoint.Client.File.OpenBinaryDirect(clientContext, fileRef);

I don't understand the root cause of this error, as I am passing client context with right access token. I want to know if OpenBinaryDirect has a limitation to work with access tokens? If not, what is wrong with above code? Is there any other alternative that can be used to download using access token?

Answer 1

Looks like an issue downloading file using Access token.

As a workaround, you can use the OpenBinaryStream method as below:

var listItems = list.GetItems(query);
clientContext.Load(listItems, items => items.Take(1).Include(item => item.File));
clientContext.ExecuteQuery();

Microsoft.SharePoint.Client.File file = listItems[0].File;
ClientResult<Stream> data = file.OpenBinaryStream();

// Load the Stream data for the file
context.Load(file);
context.ExecuteQuery();

MemoryStream memStream = new MemoryStream();
data.Value.CopyTo(memStream);

//change the path as per your requirement
string downloadedFile = @"C:\Users\Admin\Downloads\yourfile.name";

System.IO.File.WriteAllBytes(downloadedFile,memStream.ToArray());

Have tested the above code at my end seems to work for almost all major file formats(png, jpg ,docx,pdf etc.) .

Modified from - SharePoint 2013 Online App: 403 Response While Downloading Documents from a Document Library