Username argument is invalid in SharePointOnlineCredentials - CSOM

Question

I wrote a simple code in CSOM to get web title. Hope code is fine. When I execute my application I got an exception from my third line (clientContext.Credentials = new SharePointOnlineCredentials("Domain\\Username", SecurePassword);)

Username argument is invalid

Any idea to solve this issue? Thanks in advance.

using (var clientContext = new ClientContext("http://siteURL"))
{
    SecureString SecurePassword = GetSecureString("password");
    clientContext.Credentials = new SharePointOnlineCredentials("Domain\\Username", SecurePassword);
    Web web = clientContext.Web;
    clientContext.Load(web,
    webSite => webSite.Title);
    clientContext.ExecuteQuery();
    Console.WriteLine(web.Title);
}

Answer 1

The solution is very simple and clear.

While passing credentials do not use Domain name along with username. You just need to use Username.

So your code will be like:

clientContext.Credentials = new SharePointOnlineCredentials("Username", SecurePassword);

If it is SharePoint On-Prem then SharePointOnlineCredential is not required.

In such case you should use:

NetworkCredential _myCredentials = new NetworkCredential("user", "password", "domain"); // While domain will be your site url
//OR
NetworkCredential _myCredentials = new NetworkCredential(@"domain\user", "password");

and then pass credential as

clientContext.Credentials = _myCredentials;