What is the best practice to define method signature in Service oriented architecture for service call?

Question

What is the best practice to define service call prototype/signature while developing application in service oriented architecture.

For Example I want to create Service call to send email.

Let say I have following object in my domain layer

 [datacontract]
public class Email
{
      public string To { get; set; }
      public string From { get; set; }
      public string Message { get; set; }
      public string Subject { get; set; }

      //I am not going to use this properties in send email method
      public string OtherProp1 {get; set;}
      public string OtherProp2 {get; set;}
      public string OtherProp3 {get; set;}

  }

Should I create Service method signature like

   public bool SendEmail(string from,string to, string subject,string message){//My Logic}}

Or

   public bool SendEmail(Email myEmail){//My Logic}

I am leaning toward first option.(Having said that I know if object is way to complex than it make sense to pass whole object itself.)

Answer 1

Unfortunately, second option is less clear in this case and this is because of your Email class.

Suppose I am to call your method. You make me pass an instance of the Email class. I go to the class contract and find 7 properties.

And, how am I supposed to know which parameters are mandatory and which are optional? From the docs? Not a cleanest design if I have to consult the docs to make proper use of the API.

I would rather refactor your Email class to call it EmailRequest with all these optional parameters removed and then I would create yet another class EmailResponse if you ever need to use it as a return value of a service.