General code for creating an authenticated (Basic) WCF service client. IFace is the WCF interface and Clnt is the Client that inherits from ClientBase. Uses an endpoint and endpoint url when creating the client. Also uses the self-cleaning service model from ChannelAdam.

AuthenticatedWcfServiceClientBuilder.cs

using System.ServiceModel;
using ChannelAdam.ServiceModel;
using EcmServices.DataModel;

    public class User
    {
        public String Username { get; set; }
        public String Password { get; set; }
    }

    public interface IAuthenticatedWcfServiceClientBuilder<I>
    {
        I Build(User user);
    }

    public class AuthenticatedWcfServiceClientBuilder<IFace, Clnt> : IAuthenticatedWcfServiceClientBuilder<IFace> where Clnt : ClientBase<IFace> where IFace : class 
    {
        private string _endpointName;
        private string _endpointUrl;

        public AuthenticatedWcfServiceClientBuilder(string endpointName, string endpointUrl)
        {
            _endpointName = endpointName;
            _endpointUrl = endpointUrl;
        }

        public IFace Build(User user)
        {
            var consumer = ServiceConsumerFactory.Create<IFace>(() => {
                var service = (Clnt)Activator.CreateInstance(typeof(Clnt), new object[] { _endpointName, _endpointUrl });
                AddCredentials(service, user);
                return service;
            });

            return consumer.Operations;
        }

        private void AddCredentials(ClientBase<IFace> serviceClient, User user)
        {
            if (serviceClient != null && user != null && !string.IsNullOrWhiteSpace(user.Username) && !string.IsNullOrWhiteSpace(user.Password)) {
                serviceClient.ChannelFactory.Credentials.UserName.UserName = user.Username;
                serviceClient.ChannelFactory.Credentials.UserName.Password = user.Password;
            }
        }
    }
    
    public class Runner {
        public static void main(String[] args) {
            // usage assuming a LoginService interface and LoginServiceClient client
            var endpointName = "LoginClientEndpoint"
            var endpointUrl = "http://example.com/login.svc"
            var svc = new AuthenticatedWcfServiceClientBuilder<LoginService, LoginServiceClient>(endpointName, endpointUrl);
            
            var user = new User() {
                Username = "someuser",
                Password = "somepass"
            }
            
            var resp = svc.Build(user).login();
        }
    }