cefsharp windows form multiple browser tab proxy with authantication

I have a browser with multiple tabs. I want to set proxy for each tab with authantication. this is the code that i have.

CefSharpSettings.Proxy = new ProxyOptions(ip: ip, port: port, username: user, password: pass);

    if (Cef.IsInitialized != true)
    {

        Cef.Initialize(new CefSettings());
        }

    browsers = new ChromiumWebBrowser(url);

the problem is that this code allows to set proxy once. there is some solutions like this.

Cef.UIThreadTaskFactory.StartNew(delegate
{

      chrome.RequestHandler = new MyRequestHandler();

      string ip = "IP";
      string port = "PORT";
      var rc = chrome.GetBrowser().GetHost().RequestContext;
      var dict = new Dictionary<string, object>();
      dict.Add("mode", "fixed_servers");
      dict.Add("server", "" + ip + ":" + port + "");
      string error;
      bool success = rc.SetPreference("proxy", dict, out error);
});

and this class

public class MyRequestHandler : IRequestHandler
{

    bool IRequestHandler.GetAuthCredentials(IWebBrowser browserControl, IBrowser browser, IFrame frame, bool isProxy, string host, int port, string realm, string scheme, IAuthCallback callback)
    {

        if (isProxy == true)
        {             
                callback.Continue("Username", "Password");

                return true;
        }

        return false;

     }
}

but I get error on this line" public class MyRequestHandler : IRequestHandler" which tells:

Severity    Code    Description Project File    Line    Suppression State
Error   CS0535  'browser.MyRequestHandler' does not implement interface member 'IRequestHandler.OnBeforeBrowse(IWebBrowser, IBrowser, IFrame, IRequest, bool, bool)'    WindowsFormsApp1