The remote server returned an error: (401) Unauthorized (SharePoint Online & C# Application)

Question

I am trying to insert items in SharePoint online list from c# console application using CSOM method, but every time it gives me only one error:

"The remote server returned an error: (401) Unauthorized." Exception thrown: 'System.Net.WebException' in Microsoft.SharePoint.Client.dll

My question would be how can I authenticate to SharePoint online list from my C# console application?

I have checked my credentials, everything is correct still I am getting this unauthorized error.

Here is my code in c#:

Please do reply if anyone has any idea how to resolve this error!

Thanks,
Shaily

Answer 1

Context you are creating is might create issue.

Whenever you are creating the context apply the credentials like below

context = new ClientContext(siteUrl);
context.Credentials = new SharePointOnlineCredentials(login, securePassword);
context.AuthenticationMode = ClientAuthenticationMode.Default;

Post that go for creation/accessing list object or site objects.

Also:

Since you are getting 401 Authorization error, request you to verify the account and credentials you are creating have sufficient permission on the site and list.

Answer 2

Used below code :

It’s worth checking if you have site collection admin rights on the site. It’s a common misconception that if you have Global Admin rights or a SharePoint Online Admin role, You’ll automatically get admin access to SharePoint! You must add your account as a site collection administrator to each site.

string siteUrl = ConfigurationManager.AppSettings["SiteUrl"];
string clientID = ConfigurationManager.AppSettings["ClientId"];
string clientSecret = ConfigurationManager.AppSettings["ClientSecret"];
using (ClientContext clientContext = new AuthenticationManager().GetACSAppOnlyContext(siteUrl, clientID, clientSecret))
{
    List oList = clientContext.Web.Lists.GetByTitle("sDetails");
    clientContext.Load(oList);
    clientContext.Load(clientContext.Web);
    clientContext.Load(clientContext.Site);
    //clientContext.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;
    clientContext.ExecuteQuery();
}

<appSettings>
    <add key="ClientId" value="XXX-XXX-XXX-XXX-XXX" />
    <add key="ClientSecret" value="XXXXXXXXXXXXXX" />
    <add key="SiteUrl" value="https://XXXXXX.sharepoint.com/sites/XXXXXX/" />       
  </appSettings>