SharePoint Login Credential

Question

Currently I try to developed application by using SharePoint that retrieve data from List

Now I try to developed for Login Function, The error display as Below

The underlying connection was closed: An unexpected error occurred on a send.

Here with my Source Code

string WebUrl = "https://xxx.sharepoint.com/sites/devspace";
            string username = txtUsername.Text;
            string pwd = txtPassword.Text;

            ClientContext context = new ClientContext(WebUrl);
            Web web = context.Web;

            SecureString passWord = new SecureString();
            foreach (char c in pwd.ToCharArray())
                passWord.AppendChar(c);
            context.Credentials = new SharePointOnlineCredentials(username, passWord);
            try
            {
                context.Load(web);
                context.ExecuteQuery();
                lblStatus.Text = "Olla " + web.Title;

            }catch(Exception ex)
            {
                lblStatus.Text = ex.Message.ToString();
            }

Any suggestion for this? Thank in advanced.

Updated:

I'm using SharePoint 2016, login via Windows Server AD.

Answer 1

As discussed, you are using SharePoint 2016, then please download and install CSOM with SharePoint 2016 version Nuget package not SharePoint Online:

Microsoft.SharePoint2016.CSOM

And use this code snippet:

      ClientContext clientContext = new ClientContext("https://example.com/sites/testsite/");  
      clientContext.Credentials = new NetworkCredential("user", "password", "domain");
            // Get the SharePoint web  
            Web web = clientContext.Web;  

            // Get the SharePoint list collection for the web  
            ListCollection listColl = web.Lists;  

            // Retrieve the list collection properties  
            clientContext.Load(listColl);  

            // Execute the query to the server.  
            clientContext.ExecuteQuery();  

            // Loop through all the list  
            foreach (List list in listColl)  
            {  
                // Display the list title and ID  
                Console.WriteLine("List Name: " + list.Title + "; ID: " + list.Id);  
            }  
            Console.ReadLine();

SharePoint 2016 On Premise not need to use SharePointOnlineCredentials class, just pass username, password, domain as code snippet above.