"An invalid argument was supplied" error when I try to connect sharepoint online using SharePoint Client Object Model with .NET application

Question

I am trying to connect SharePoint online (office 365 cloud base) through c#.net code.I am using "Microsoft.SharepointOnline.CSOM" Nuget package version V16.1.7414.1200 and application .net framework 4.5.2. I already tried all different type of code by looking on google. nothing is working for me. Here I put all the sample codes, I tried. Sample code 1

using (ClientContext clientContext = new ClientContext(“https://example.com”))
        {
            var psd = "password".ToCharArray();
            SecureString secureString = new SecureString();
            foreach (char c in psd) secureString.AppendChar(c);
            //psd.ToList().ForEach(secureString.AppendChar);

            clientContext.Credentials = new SharePointOnlineCredentials("username", secureString);
           // Web oWeb = clientContext.Web;
           List oList = clientContext.Web.Lists.GetByTitle("Title");

            CamlQuery camlQuery = new CamlQuery();
            camlQuery.ViewXml = "<View><RowLimit>100</RowLimit></View>";

            ListItemCollection collListItem = oList.GetItems(camlQuery);

            clientContext.Load(collListItem,
            items => items.Include(
                item => item.Id,
                item => item.DisplayName,
                item => item.HasUniqueRoleAssignments));

            clientContext.ExecuteQuery();

            foreach (ListItem oListItem in collListItem)
            {
                Console.WriteLine(@"ID: {0} \nDisplay name: {1} \nUnique role assignments: {2}",
                oListItem.Id, oListItem.DisplayName, oListItem.HasUniqueRoleAssignments);
            }
        }

Sample Code 2

using (ClientContext spcontext = new ClientContext(siteurl))
        {
            spcontext.AuthenticationMode = ClientAuthenticationMode.FormsAuthentication;
            spcontext.FormsAuthenticationLoginInfo = new FormsAuthenticationLoginInfo("username", "password");
            spcontext.Load(spcontext.Web, w => w.Title, w => w.ServerRelativeUrl, w => w.Lists);
            try
            {
                spcontext.ExecuteQuery();
                Console.WriteLine(spcontext.Web.ServerRelativeUrl);
            }
            catch (Exception ex)
            {

                //throw;
            }


        }

Sample Code 3

 using (ClientContext clientContext = new ClientContext(webSPOUrl))
        {


            clientContext.Credentials = new SharePointOnlineCredentials(userName, passWord);

            Web web = clientContext.Web;

            clientContext.Load(web);
            try
            {
                clientContext.ExecuteQuery();
            }
            catch (Exception ex)
            {

                Debug.WriteLine(ex.Message);
            }


            //Console.WriteLine(web.Title);

            //Console.ReadLine();
        }

I am getting the error for ".ExecuteQuery()" all the times on all sample codes.FYI- there is no proxy setting on my machine

"Error creating the Web Proxy specified in the 'system.net/defaultProxy' configuration section."}

So I also change the default proxy setting in my app.config file.

<system.net>
<defaultProxy enabled="false" useDefaultCredentials="false">
  <proxy/>
  <bypasslist>
    <add address="[a-z]+\.[a-z]+\.[a-z]+" />
  </bypasslist>
  <module/>
</defaultProxy>

But after above config setting changes, I am getting the error. The underlying connection was closed: Unable to connect to the remote server. Inner exception for all the times is as below. {"An invalid argument was supplied"} -2147467259

Code reference is from below URL https://learn.microsoft.com/en-us/sharepoint/dev/sp-add-ins/complete-basic-operations-using-sharepoint-client-library-code

Answer 1

Is there Proxy server in your network environment?

If there is, we need to set the IP and port of proxy server as below.

<system.net>
 <defaultProxy>
   <proxy proxyaddress="http://[Proxy IP Address]:[Proxy Port Number]" bypassonlocal="True" />
 </defaultProxy>

In another way, we can modify the HOST file to specify the IP address and domain name.

Familiar thread for your reference:

The remote name could not be resolved: '*****online.sharepoint.com' in O365 Online Sharepoint in ASP.net