Is it possible to login to SharePoint Online in Microsoft.SharePointOnline.CSOM C# background service, using a secret key?

Question

We are using SharePoint Online as a DMS in our application. Currently we have created a user for SharePoint and using his credentials we are uploading the documents to SharePoint using Microsoft.SharePointOnline.CSOM C# background service. But we need to upload documents on behalf of other users. Is it possible to do so using a secret key?

Answer 1

Hi @Dona Maria ,

According to my research and testing, you can connect to SharePoint Online using Client ID/ Client Secret via CSOM. First, you need to set up an app-only principal with tenant permissions, please follow the steps in this document: Granting access using SharePoint App-Only.

Then use the following code to connect to SharePoint Online:

string siteUrl = "https://contoso.sharepoint.com/sites/demo";  
using (var cc = new AuthenticationManager().GetACSAppOnlyContext(siteUrl, "[Your Client ID]", "[Your Client Secret]"))  
{  
    cc.Load(cc.Web, p => p.Title);  
    cc.ExecuteQuery();  
    Console.WriteLine(cc.Web.Title);  
};  

If you want to upload documents to SharePoint Online, please use the following code:

public void UploadDocumentContentStream(ClientContext ctx, string libraryName, string filePath)  
{  
  Web web = ctx.Web;  
  
  using (FileStream fs = new FileStream(filePath, FileMode.Open))  
  {  
    FileCreationInformation flciNewFile = new FileCreationInformation();  
  
    // This is the key difference for the first case - using ContentStream property  
    flciNewFile.ContentStream = fs;  
    flciNewFile.Url = System.IO.Path.GetFileName(filePath);  
    flciNewFile.Overwrite = true;  
  
    List docs = web.Lists.GetByTitle(libraryName);  
    Microsoft.SharePoint.Client.File uploadFile = docs.RootFolder.Files.Add(flciNewFile);  
  
    ctx.Load(uploadFile);  
    ctx.ExecuteQuery();  
  }  
}  

Here is my test code and test result, you can refer to it:

static void Main(string[] args)  
        {  
            string siteUrl = "https://xxxxx.sharepoint.com/sites/zella";  
            using (var cc = new AuthenticationManager().GetAppOnlyAuthenticatedContext(siteUrl, "[Your Client ID]", "[Your Client Secret]"))  
            {  
                cc.Load(cc.Web, p => p.Title);  
                cc.ExecuteQuery();  
                Debug.WriteLine(cc.Web.Title);  
                Web web = cc.Web;  
  
                string libraryName = "LibraryTest";  
                string filePath = "C:/Temp/1124.txt";  
  
  
                using (FileStream fs = new FileStream(filePath, FileMode.Open))  
                {  
                    FileCreationInformation flciNewFile = new FileCreationInformation();  
  
                    // This is the key difference for the first case - using ContentStream property  
                    flciNewFile.ContentStream = fs;  
                    flciNewFile.Url = System.IO.Path.GetFileName(filePath);  
                    flciNewFile.Overwrite = true;  
  
                    List docs = web.Lists.GetByTitle(libraryName);  
                    Microsoft.SharePoint.Client.File uploadFile = docs.RootFolder.Files.Add(flciNewFile);  
  
                    cc.Load(uploadFile);  
                    cc.ExecuteQuery();  
                }  
            }  
  
        }  

More information for reference: Upload large files sample SharePoint Add-in

Hope it can help you. Thanks for your understanding.

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Answer 2

Hi Tong,

I tested above code with Pnp.framework i.e. with GetACSAppOnlyContext on .net 6.

I am able to get the web.title, which means I am having the permissions.

However while uploading the document its giving below error. The Admin informed I have been provided full permission for this site collection. Please suggest. Could there be a way to programmatically display permission level of my client id/client secret or could it be issue with Initializing/loading of the fields of folders/files.

Best Regard,

Shiva