Unity Container usage With multiple implementation - unity-container

Question

I have come up with a Question, that what is the usage of Unity Container or NInject if it is handled only for a single instance of an interface.
Ex: Generally we use like this
Public Class IEmailSender
{
Public Void SendEmail();
}
Public Class SMTP: IEmailSender
{
Public Void SendEmail()
{
// Send Email Logic using SMTP
}
}
Public Class OtherSender: IEmailSender
{
Public Void SendEmail()
{
// Send Email Logic for Other Sender
}
}
Public Class Builder
{
Public Static IEmailSender CreateBuilder(string senderType)
{
if(senderType.Equals("SMTP"))
{
Return New SMTP();
}
ElseIf(senderType.Equals("OTHER"))
{
Return New OtherSender();
}
}
}
In my Screen have two buttons
#1. Send from SMTP - Event(EventArgs)
#2. Send from Other Sender - Event(EventArgs)
Have the Same Logic in two Methods
IEmailSender emailSender = Builder.CreateBuilder(button.CommandArgument)
emailSender.sendEmail();
So, How these different scenarios will be handled with Unity Configuration in Unity Block
or NInject Binder,
Your feedback will be highly appreciatable.

Answer 1

In Unity, You can use named instances to register and retrieve different implementations of a single interface.
First You need to register concrete types to the interface using apriopriate names:
var container = new UnityContainer();
container.RegisterType<IEmailSender, SmtpSender>("SMTP");
container.RegisterType<IEmailSender, OtherSender>("OTHER");
After this you can use it in Your code:
IEmailSender emailSender = container.Resolve<IEmailSender>(button.CommandArgument);
emailSender.SendEmail();