问重构C#代码(帮助改进)

EN

public override void Body(object _obj, object _objInPreviousState)
        {

            if (_obj != null)
            {
                string Message = "";
                string Subject = "";
                if (_objInPreviousState == null)
                {
                    var emailParams = this.Param as Dictionary<string, string>;
                    if (emailParams != null)
                    {
                        Message = emailParams["Message"];
                        Subject = emailParams["Subject"];
                    }
                }
                var emails = userRepository().GetForRoles("RM").Select(c => c.Email);
                if (_obj is Application)
                {
                    var app = (Application)_obj;
                    var appInPreviousState = _objInPreviousState as Application;
                    if (appInPreviousState == null)
                    {
                        emailService().SendEmails("aps@somedomain.com", emails.ToArray(), Message, Subject);
                    }
                    else if (app.ApplicationStatus != appInPreviousState.ApplicationStatus)
                    {
                        emailService().SendEmails("aps@somedomain.com", emails.ToArray(), "Application: " + 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 prodInPreviousState = _objInPreviousState as Product;
                    if (prodInPreviousState == null)
                    {
                        emailService().SendEmails("aps@somedomain.com", emails.ToArray(), Message, Subject);
                    }
                    else if (product.ProductStatusType != prodInPreviousState.ProductStatusType)
                    {
                        emailService().SendEmails("aps@somedomain.com", emails.ToArray(), "Product: " + product.ID + " for application " + 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;
                    var cesInPreviousState = _objInPreviousState as CES;
                    if (cesInPreviousState == null)
                    {
                        emailService().SendEmails("aps@somedomain.com", emails.ToArray(), Message, Subject);
                    }
                    else if (ces.Status != cesInPreviousState.Status)
                    {
                        emailService().SendEmails("aps@somedomain.com", emails.ToArray(), "CES for application " + 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;
                    emailService().SendEmails("aps@somedomain.com", emails.ToArray(), "Comment for the following application: " + comment.ApplicationID + " with message: " + comment.Message + " on date: " + comment.CreatedDate, "Comment for the following application: " + comment.ApplicationID);
                }
                mLog.InfoLine("Sendet Email");
            }

        }