new ServiceReference1.Service1SoapClient().HelloMom("Bob");

class Program
{
    private static bool customValidation(object s, X509Certificate c, X509Chain ch, SslPolicyErrors e)
    { return true }

    static void Main(string[] args)
    {
         // accept anything
        ServicePointManager.ServerCertificateValidationCallback +=
              new RemoteCertificateValidationCallback(customValidation);

        var binding = new BasicHttpBinding(BasicHttpSecurityMode.Transport);
        binding.Security.Transport.ClientCredentialType = HttpClientCredentialType.Basic;
        binding.Security.Transport.Realm = "Secured area";

        // the generated Web Service Reference class
        var client = new ServiceReference1.Service1SoapClient(
            binding,
            new EndpointAddress("https://smplsite.com/sandbox3/Service1.asmx")
            );

        client.ClientCredentials.UserName.UserName = "testapp";
        client.ClientCredentials.UserName.Password = "testpw";

        Console.WriteLine(client.HelloMom("Bob"));
    }
}

MyWebService svc = new MyWebService();
svc.Credentials = new System.Net.NetworkCredential(UserID, pwd);
bool result = svc.MyWebMethod();

public class MyWebService : System.Web.Services.WebService
{
    public AuthenticationHeader AuthenticationInformation;

    public class AuthenticationHeader : SoapHeader
    {
        public string UserName;
        public string Password;
    }

    [WebMethod( Description = "Sample WebMethod." )]
    [SoapHeader( "AuthenticationInformation" )]
    public bool MyWebMethod()
    {
        if ( AuthenticationInformation != null )
        {
            if ( IsUserAuthenticated( AuthenticationInformation.UserName,
                 AuthenticationInformation.Password, ref errorMessage ) )
            {
                 // Authenticated, do something
            }
            else
            {
                 // Failed Authentication, do something
            }
        }
        else
        {
                 // No Authentication, do something
        }
    }
}

MyWebService svc = new MyWebService();
 svc.AuthenticationHeaderValue = new MyWebService.AuthenticationHeader();
 svc.AuthenticationHeaderValue.UserName = UserID;
 svc.AuthenticationHeaderValue.Password = Password;

 bool result = svc.MyWebMethod();

<binding name="MyBinding" closeTimeout="00:00:30"
      openTimeout="00:00:30" receiveTimeout="00:00:30" sendTimeout="00:00:30"
      allowCookies="false" bypassProxyOnLocal="false" hostNameComparisonMode="StrongWildcard"
      maxBufferPoolSize="524288" maxBufferSize="2147483647" maxReceivedMessageSize="2147483647"
      textEncoding="utf-8" transferMode="Buffered" useDefaultWebProxy="true"
      messageEncoding="Text">
      <readerQuotas maxDepth="32" maxStringContentLength="2147483647"
        maxArrayLength="2147483647" maxBytesPerRead="4096" maxNameTableCharCount="16384" />
      <security mode="Transport">
        <transport clientCredentialType="Basic" realm=""/>
      </security>
    </binding>
  </basicHttpBinding>

proxy.ClientCredentials.UserName.UserName = userName;
proxy.ClientCredentials.UserName.Password = password;