How to download files from SharePoint online using the.net WebClient

[JRDTechnologies]

I'm trying to download files from SharePoint online using the.net 4.8 WebClient and the Microsoft.SharePointOnline.CSOM package. Here is sample code, what am I doing wrong?

string uid = "myusername@domain.com";
string pwd = "mypassword";
string url = "https://tenant.sharepoint.com/:b:/r/filepath.pdf";
var sp = new SecureString();
foreach (var c in pwd.ToCharArray())
{
    sp.AppendChar(c);
}
var cred= new SharePointOnlineCredentials(uid, sp);
using (var cl = new WebClient())
{
    cl.Credentials = credentials;
    cl.Headers.Add("X-FORMS_BASED_AUTH_ACCEPTED", "f");
    cl.DownloadFile(url, "C:\\temp\\Hello.docx); 
}

I'm getting a 401 Unauthorized error. To double-check that my credentials were right, I logged out and back into the SharePoint environment using the same credentials.

To test if it helps, I added a few of other user agents to the header.

cl.Headers.Add("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");
also tried...
cl.Headers.Add("User-Agent: Other");