Sending email based on object type

Question

This is one of a classes (that sends email based on object type to AM (role)) that is executed by an engine. I also have commands like SendEmailToAOCommand that send email to a role AO based on object type and so one.

namespace SFE.Workflow.Commands
{
    public class SendEmailToAMCommand : ActionCommand
    {
        private readonly Func<IApplicationRepository> applicationRepository;
        private readonly IClientRepository clientRepository;
        private readonly Func<IEmailService> emailService;
        private readonly Func<IUserRepository> userRepository;


        public SendEmailToAMCommand(
            Func<IEmailService> _emailService,
            Func<IUserRepository> _userRepository,
            Func<IApplicationRepository> _applicationRepository,
            IClientRepository _clientRepository)
        {
            emailService = _emailService;
            CommandFor = Modules.All;
            userRepository = _userRepository;
            applicationRepository = _applicationRepository;
            clientRepository = _clientRepository;
        }

        public override string CommandDescription
        {
            get { return "Sends email to AM"; }
        }

        public override void Body(object _obj, object _objInPreviousState)
        {
            if (_obj == null)
                throw new ArgumentNullException("first param is null");

            string message = string.Empty;
            string subject = string.Empty;
            if (_objInPreviousState == null)
            {
                var emailParams = Param as Dictionary<string, string>;
                if (emailParams != null)
                {
                    message = emailParams["Message"];
                    subject = emailParams["Subject"];
                }
            }
            if (_obj is Application)
            {
                var app = (Application)_obj;
                var email = userRepository().GetManagerForUser(app.UserID).Email;
                Client borrower = clientRepository.GetMainBorrower(app.ID);
                if (_objInPreviousState == null)
                {
                    emailService().SendEmail("", email, message, subject);
                }
                else
                {
                    emailService().SendEmail("", email,"Application: " + borrower.CompanyName + " (" + app.ID +") changed decision status: " +Enum.GetName(typeof(AppStatus), app.ApplicationStatus),"Check following application: " + app.ID);
                }
            }
            else if (_obj is Product)
            {
                var product = (Product)_obj;
                var email = userRepository().GetManagerForUser(product.Application.UserID).Email;
                Client borrower = clientRepository.GetMainBorrower(product.ApplicationID);
                if (_objInPreviousState == null)
                {
                    emailService().SendEmail("", email, message, subject);
                }
                else
                {
                    emailService().SendEmail("", email,"Product: " + product.ID + " for application " + borrower.CompanyName +" (" + product.ApplicationID + ") changed decision status: " +Enum.GetName(typeof(AppStatus), product.ProductStatusType),"Check following application: " + product.ApplicationID);
                }
            }

            else if (_obj is CES)
            {
                var ces = (CES)_obj;
                User user = applicationRepository().GetByID(ces.ApplicationID).User;
                var email = userRepository().GetManagerForUser(user.UserName).Email;
                Client borrower = clientRepository.GetMainBorrower(ces.ApplicationID);
                if (_objInPreviousState == null)
                {
                    emailService().SendEmail("", email, message, subject);
                }
                else
                {
                    emailService().SendEmail("", user.Email,"CES for application " + borrower.CompanyName + " (" +ces.ApplicationID + ") changed decision status: " +Enum.GetName(typeof(CesStatuses), ces.Status),"Check following application: " + ces.ApplicationID);
                }
            }
            else if (_obj is Comment)
            {
                var comment = (Comment)_obj;
                Client borrower = clientRepository.GetMainBorrower(comment.ApplicationID);
                emailService().SendEmail("", comment.User.Email,"Comment for the following application: " + borrower.CompanyName + " (" +comment.ApplicationID + ") with message: " + comment.Message + " on date: " +comment.CreatedDate,"Comment for the following application: " + comment.ApplicationID);
            }
            else if (_obj is Memo)
            {
                var memo = (Memo)_obj;
                var email = userRepository().GetManagerForUser(memo.UserID).Email;
                Client borrower = clientRepository.GetMainBorrower(memo.ApplicationID);
                if (_objInPreviousState == null)
                {
                    emailService().SendEmail("", email, message, subject);
                }
                else
                {
                    emailService().SendEmail("", email, "Memo for application : " + borrower.CompanyName + " (" + memo.ApplicationID + ") changed decision status: " + Enum.GetName(typeof(AppStatus), memo.Status), "Check following memo for application: " + memo.ApplicationID);
                }
            }
            Logger.InfoLine("Sending Email done" + " @" + CommandName);

        }
    }
}

The problem: this pattern is used in all of other commands. How can I improve this so this will not have same code in over and over again?

Answer 1

You don't provide any example of how SendEmailToAOCommand would differ from SendEmailToAMCommand, so I can't be more specific, but here's the gist of what you should do:

public abstract class SendEmailBase : ActionCommand
{
    private readonly Func<IApplicationRepository> applicationRepository;
    private readonly IClientRepository clientRepository;
    private readonly Func<IEmailService> emailService;
    private readonly Func<IUserRepository> userRepository;


    public SendEmailBase(
        Func<IEmailService> _emailService,
        Func<IUserRepository> _userRepository,
        Func<IApplicationRepository> _applicationRepository,
        IClientRepository _clientRepository)
    {
        emailService = _emailService;
        CommandFor = Modules.All;
        userRepository = _userRepository;
        applicationRepository = _applicationRepository;
        clientRepository = _clientRepository;
    }

    public override string CommandDescription
    {
        get { return "Sends email to " + EmailRecipient; }
    }
    public abstract string EmailRecipient { get; }

    public override void Body(object _obj, object _objInPreviousState)
    {
        if (_obj == null)
            throw new ArgumentNullException("first param is null");

        string message = string.Empty;
        string subject = string.Empty;
        if (_objInPreviousState == null)
        {
            var emailParams = Param as Dictionary<string, string>;
            if (emailParams != null)
            {
                message = emailParams["Message"];
                subject = emailParams["Subject"];
            }
        }
        if (_obj is Application)
        {
            var app = (Application)_obj;
            var email = userRepository().GetManagerForUser(app.UserID).Email;
            Client borrower = clientRepository.GetMainBorrower(app.ID);
            if (_objInPreviousState == null)
            {
                emailService().SendEmail("", email, message, subject);
            }
            else
            {
                emailService().SendEmail("", email,"Application: " + borrower.CompanyName + " (" + app.ID +") changed decision status: " +Enum.GetName(typeof(AppStatus), app.ApplicationStatus),"Check following application: " + app.ID);
            }
        }
        else if (_obj is Product)
        {
            var product = (Product)_obj;
            var email = userRepository().GetManagerForUser(product.Application.UserID).Email;
            Client borrower = clientRepository.GetMainBorrower(product.ApplicationID);
            if (_objInPreviousState == null)
            {
                emailService().SendEmail("", email, message, subject);
            }
            else
            {
                emailService().SendEmail("", email,"Product: " + product.ID + " for application " + borrower.CompanyName +" (" + product.ApplicationID + ") changed decision status: " +Enum.GetName(typeof(AppStatus), product.ProductStatusType),"Check following application: " + product.ApplicationID);
            }
        }

        else if (_obj is CES)
        {
            var ces = (CES)_obj;
            User user = applicationRepository().GetByID(ces.ApplicationID).User;
            var email = userRepository().GetManagerForUser(user.UserName).Email;
            Client borrower = clientRepository.GetMainBorrower(ces.ApplicationID);
            if (_objInPreviousState == null)
            {
                emailService().SendEmail("", email, message, subject);
            }
            else
            {
                emailService().SendEmail("", user.Email,"CES for application " + borrower.CompanyName + " (" +ces.ApplicationID + ") changed decision status: " +Enum.GetName(typeof(CesStatuses), ces.Status),"Check following application: " + ces.ApplicationID);
            }
        }
        else if (_obj is Comment)
        {
            var comment = (Comment)_obj;
            Client borrower = clientRepository.GetMainBorrower(comment.ApplicationID);
            emailService().SendEmail("", comment.User.Email,"Comment for the following application: " + borrower.CompanyName + " (" +comment.ApplicationID + ") with message: " + comment.Message + " on date: " +comment.CreatedDate,"Comment for the following application: " + comment.ApplicationID);
        }
        else if (_obj is Memo)
        {
            var memo = (Memo)_obj;
            var email = userRepository().GetManagerForUser(memo.UserID).Email;
            Client borrower = clientRepository.GetMainBorrower(memo.ApplicationID);
            if (_objInPreviousState == null)
            {
                emailService().SendEmail("", email, message, subject);
            }
            else
            {
                emailService().SendEmail("", email, "Memo for application : " + borrower.CompanyName + " (" + memo.ApplicationID + ") changed decision status: " + Enum.GetName(typeof(AppStatus), memo.Status), "Check following memo for application: " + memo.ApplicationID);
            }
        }
        Logger.InfoLine("Sending Email done" + " @" + CommandName);

    }
}

public class SendEmailToAMCommand : SendEmailBase
{
    public SendEmailToAMCommand(
             Func<IEmailService> _emailService,
             Func<IUserRepository> _userRepository,
             Func<IApplicationRepository> _applicationRepository,
             IClientRepository _clientRepository) : base(_emailService, _userRepository, _applicationRepository, _clientRepository) { }
    public override string EmailRecipient { get { return "AM"; } }
}

Everything that's the same gets put into SendEmailBase. Everything which could vary is defined as an abstract method or property, and then the subclasses implement just those things which make it different.