Trigger to prevent deletion of account if account has atleast one contact associated with it using trigger

Question

Below is my code but dont know how to validate it exactly in code.new to code

trigger AccountContactCheck on Account (before delete) {
Set<id> accountids=new set<id>();
for(account acc:trigger.old){
    accountids.add(acc.id);
}Map<id,contact>conmap=new map<id,contact>([select accountid from contact where accountid in :accountids]);
System.debug('conmap>>>>'+conmap.keySet());
for(account acc:trigger.old){
    if(conmap.get(acc.id)!=null){
        System.debug('Inside If of account >>>>>>');
        acc.adderror('Contact is associated with it.you cant delete account');

    }
}

Answer 1

You have did mistake while capture conmap Map, In conmap your storing key id as contact id and value as accountid.

if(conmap.get(acc.id)!=null)

In the above code your match account id with contact id , ie.. the reason if condition always be false in your case, your not able go inside if condition.

Try below code it will work for you.

You can use group by clause make shorten in code

trigger AccountContactCheck on Account (before delete) {   
for (AggregateResult ar : [SELECT accountid, count(id)size  FROM contact where accountid in : Trigger.oldMap.keySet() GROUP BY accountid])
    if(((integer)ar.get('size'))>0)
         trigger.oldMap.get((id)ar.get('accountid')).adderror('******* Contact is associated with it.you cant delete account');         
}

OR

Alternate

 trigger AccountContactCheck on Account (before delete) { 
        List<contact> Contacts = [select accountid from contact where accountid in : Trigger.oldMap.keySet()];
        set<id> accIds=new set<id>();
          for(contact con: Contacts)
                 accIds.add(con.accountid);

        for(account acc:trigger.old)
            if(accIds.contains(acc.id))
                acc.adderror('******* Contact is associated with it.you cant delete account');            
    }