[Deepanshu Singh]

I don't know what exactly you are trying to do. Please be more brief, Anyways, wrapper class instance can be added easily in list by these few statements. List<wrapperClass> wrapClassList = new List<wrapperClass>();
wrapClassList.add(new wrapperClass(arg1, arg2)());

[Deepanshu Singh]

Goto App Manager > select lightning app > add your lightning page > finish

[Deepanshu Singh]

It is done to improve the readability and cleanliness of the code

[Deepanshu Singh]

Recursive Trigger problem occurs usually on update Trigger, you have solve the problem by adding this code :

public class CheckRecursive {
    private static boolean run = true;
    public static boolean runOnce() {
        if(run) {
            run = false;
            return true;
        }
        else {
            return run;   
        } 
    }
}

if((Trigger.isBefore || Trigger.isAfter) && Trigger.isUpdate ))

{

if(CheckRecursive.runOnce()) {

// your further code here

}

}

[Deepanshu Singh]

Avoid the inner Queries, follow the best practices

[Deepanshu Singh]

For the Aggregate Query you have AggregateResult class in apex

Example

for(AggregateResult ar : [select count(Id), AccountId
                          from Contact 
                          where AccountId in :accset
                          group by AccountId
                          having count(Id)>2 ])
{
    contList.add(new Contact(Id = (ID)ar.get('AccountId')));
}
try{
    update contList;
}catch(DMLException exc){
    system.debug("Exception => " + exc.getMessage());
}

 

[Deepanshu Singh]

Go to Quick Find, type duplicate Rules , untick the old rules or create a new Rule which defines duplicate not allowed

[Deepanshu Singh]

set<id> accountids = new set<id>();
for(Contact con : Trigger.New) {        
     accountids.add(con.AccountId);
}
List<account> accList = [ select Name, (select AccountId, firstName, lastName from Contacts where AccountId =: accountids limit 1) from Account ];