How to restrict duplicate emails entering into loop?

Question

Could anyone help on this issue.

In the below apex class I have method called getWrapAccounts().In this method for loop allows duplicate values.I have a Login__c field,It is emailID based on thid id how can I avoid duplicate emails entering into loop.

public with sharing class WebinarDetailsExtension {

    public String pageId = Apexpages.currentPage().getParameters().get('id'); 
    public List<Webinar__c> ws = new List<Webinar__c>();
    public List<WebinarAttendeesWrapper> WebinarAttendeesWrapperList = new List<WebinarAttendeesWrapper>(); 
    public String popupvalue{get; set;}  
    list<Webinar_Attendees__c> selectedContacts = new list<Webinar_Attendees__c>();


    public WebinarDetailsExtension(Apexpages.StandardController stdcController){        
        Webinar__c w = [select id,Name,Start_Time__c,Finish_Time__c,Registration_URL__c,Expired__c from Webinar__c where id = : pageId];        
        eventid = w.SCO_ID__c;
        eventName = w.Id;       
        ws.add(w);                        

    }

    //Get list of Attendees of the Webinar
    public List<WebinarAttendeesWrapper> getWrapAccounts() {                     
        List<Webinar_Attendees__c> ld =  [select Id,Name,principal_id__c,Login__c,isLead__c,Attandance_Status__c,Duration_Spend__c,Company_Name__c,City__c,
                                          State__c,Country__c,Opportunity__c,Mobile_Phone__c,WebinarContact__c,Salesforce_Lead__c,Email_Sent__c,Voucher_Number__c,
                                          Voucher_Number__r.Name from Webinar_Attendees__c where Webinar__c = : pageId AND CreatedDate <= TODAY 
                                          ORDER BY LastModifiedDate DESC NULLS FIRST LIMIT : limitsize OFFSET : count ];          

        // this prints two records          
        system.debug('list of attendees:: '+ ld);                   


        //Here "Login__c" is an email address.only unic email id's enterig into loop.


        for (Webinar_Attendees__c aa : ld) { 

            //how to set a condition for to avoid duplicates
            If(Login__c){

                WebinarAttendeesWrapperList.add(new WebinarAttendeesWrapper(aa));                                                                 
            }
        }  
        //This prints 6 records ,each record prints 2 times.duplicates are added
        system.debug('WebinarAttendeesWrapperList 2:: '+  WebinarAttendeesWrapperList);                         
        return WebinarAttendeesWrapperList;
    } 

    //Wrapper class
    public class WebinarAttendeesWrapper {            
        public Webinar_Attendees__c acc {get; set;}
        public Boolean selected {get; set;}

        public WebinarAttendeesWrapper(Webinar_Attendees__c a){
            acc = a;
            selected = false;
        }      
    }    

}

Answer 1

You should maintain a list containing unique e-mail ids and before adding items in WebinarAttendeesWrapperList. Check if that list contains e-mail id or not before populating WebinarAttendeesWrapperList.

Something like this

List<String> uniqueEmailIdList = new List<String>();
for (Webinar_Attendees__c aa : ld) { 

        //how to set a condition for to avoid duplicates
        If( !uniqueEmailIdList.contains(Login__c)){//If uniqueEmailIdList does not contain the e-amil id then udpate WebinarAttendeesWrapperList
             uniqueEmailIdList.add( Login__c );//Add the new e-mail id to uniqueEmailIdList so WebinarAttendeesWrapperList is not added with object having the duplicate e-mail id
             WebinarAttendeesWrapperList.add(new WebinarAttendeesWrapper(aa));                                                                 
    }

Answer 2

just a change in above answer

List<String> uniqueEmailIdList = new List<String>();

for (Webinar_Attendees__c aa : ld) { 

    If(!uniqueEmailIdList.contains(aa.Login__c)){
    uniqueEmailIdList.add(aa.Login__c );
    WebinarAttendeesWrapperList.add(new WebinarAttendeesWrapper(aa));                                                                 

}