C#

public interface IAmInterface
   {
       string Method(string username, string password);

   }

public class Service : IAmInterface
    {
    public string Method(string username, string password)
    {
       
     return "Some string";
    }
}

public class SomeClass
{

private readonly IAmInterface _name;

public SomeClass(IAmInterface userinterface)

        {
            _name = userinterface;

        }

public void Method2
{
var name1=_name.Method("a","b");
}
}

try
        {
            MailMessage mail = new MailMessage();


            mail.From = new MailAddress("sami.goswami@gmail.com");
            mail.To.Add(txtto.Text);
            mail.Subject = txtsub.Text;
            mail.Body = txtmsg.Text;

            SmtpClient Smtpserver = new SmtpClient();

            Smtpserver.Credentials = new NetworkCredential("sami.goswami@gmail.com", "password", "smtp.gmail.com");
            Smtpserver.Host = "smtp.gmail.com";
            Smtpserver.Port = 587;
            Smtpserver.DeliveryMethod = SmtpDeliveryMethod.Network;

            Smtpserver.EnableSsl = true;
            Smtpserver.UseDefaultCredentials = false;

            Smtpserver.Send(mail);


            label1.Text = "Email successfully sent";
        }
        catch (Exception ex)
        {
            label1.Text = "Email failed" + ex.Message;
        }

<pre lang="XML"><configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.5"/>
    <httpRuntime targetFramework="4.5"/>
  
  </system.web>
<system.net>
            <mailSettings>
                <smtp deliveryMethod="Network" from="sami.goswami@gmail.com">
                    <network defaultCredentials="false" host="smtp.gmail.com" port="25" userName="sami.goswami@gmail.com" password="password"/>
                </smtp>
            </mailSettings>
        </system.net>
</configuration>

<pre lang="c#">

PaperSize paperSize = new PaperSize("Custom", Current_Paper_Width, Current_Paper_Height);

                            paperSize.RawKind = (int)PaperKind.Custom;

                            Current_setting.PaperSize = paperSize;

                            printDocument1.DefaultPageSettings = Current_setting;

static void Main(string[] args)
{
    Thread cleanupThread = new Thread(cleanupThreadStart);
    cleanupThread.Start(Thread.CurrentThread);
    Thread.Sleep(5000);
    Console.WriteLine("Main: Ended.");
}

private static void cleanupThreadStart(object state)
{
    Thread mainThread = (Thread)state;
    Console.WriteLine("cleanupThreadStart: Waiting for main thread to exit.");
    mainThread.Join();
    Console.WriteLine("cleanupThreadStart: Ended.");
}