public class sampleConSubmissions {
    
     String[] submissions = new String[]{};

    public sampleConSubmissions(ApexPages.StandardController controller) {

    }
        
            
        public PageReference test() {
            return null;
        }
            
        public List<SelectOption> getItems() {
            List<SelectOption> options = new List<SelectOption>();
            options.add(new SelectOption('TR00025712016 - Umbr only','TR00025712016 - Umbr only'));
            options.add(new SelectOption('TR00028982016 - Casualty','TR00028982016 - Casualty'));
            options.add(new SelectOption('TR18622016 - Casualty','TR18622016 - Casualty'));
            options.add(new SelectOption('TR20612016 - Property','TR20612016 - Property'));
            return options;
        }
            
        public String[] getsubmissions() {
            return submissions;
        }
            
        public void setsubmissions(String[] submissions) {
            this.submissions = submissions;
        }
    }

<apex:selectList value="{!submissions}" multiselect="true">
            <apex:selectOptions value="{!items}"/>
        </apex:selectList><p/>

        <apex:commandButton value="Select Submissions" action="{!test}" rerender="out" status="status"/>
    

    <apex:outputPanel id="out">
        <apex:actionstatus id="status" startText="testing...">
            <apex:facet name="stop">
                <apex:outputPanel >
                    <p>You have selected:</p>
                    <apex:dataList value="{!submissions}" var="c">{!c}</apex:dataList>
                </apex:outputPanel>
            </apex:facet>
        </apex:actionstatus>
    </apex:outputPanel>

Trigger :
----------

if(Trigger.isDelete){
                
   Database.executeBatch(new BatchUpdateAcct(Trigger.OldMap),1);
               
}

Batch Class
-------------

global class BatchUpdateAcct implements Database.Batchable<sObject> {
    
    Map<Id,Object__c> mapRecs = new Map<Id,Object__c>();
    
    global BatchUpdateAcct(Map<Id,Object__c> oldValue){
        mapRecs = oldValue;
       
    }
    
    global Database.QueryLocator start (Database.BatchableContext BC){
        System.debug('----Start Method-----'+mapRecs.keySet());
        return Database.getQueryLocator([Select id,Name from Object__c where id in :mapRecs.KeySet()]);
    }
    
    global void execute (Database.BatchableContext BC, List<Object__c> objList){
        
    }
    
    global void finish(Database.BatchableContext BC){
        
    }

}

Trigger :
----------

if(Trigger.isDelete){
                
   Database.executeBatch(new BatchUpdateAcct(Trigger.OldMap),1);
               
}

Batch Class
-------------

global class BatchUpdateAcct implements Database.Batchable<sObject> {
    
    Map<Id,Object__c> mapRecs = new Map<Id,Object__c>();
    
    global BatchUpdateAcct(Map<Id,Object__c> oldValue){
        mapRecs = oldValue;
       
    }
    
    global Database.QueryLocator start (Database.BatchableContext BC){
        System.debug('----Start Method-----'+mapRecs.keySet());
        return Database.getQueryLocator([Select id,Name from Object__c where id in :mapRecs.KeySet()]);
    }
    
    global void execute (Database.BatchableContext BC, List<Object__c> objList){
        
    }
    
    global void finish(Database.BatchableContext BC){
        
    }

}

Handler class
-------------------------
public with sharing class ClientHandlerCtrl {
    
    public static boolean insertRecursiveStop = true;
    public static boolean updateRecursiveStop = true;
    
    public static void ClientInsert(Map<Id,Client__c> newMap){
        
        try{
            Set<String> usrName = new Set<String>();
        
            for(ID clientIds : newMap.keySet()){
                            
                Client__c client = newMap.get(clientIds);
                if(client.Client_Manager__c != Null){
                    usrName.add(client.Client_Manager__c);
                }
            }
            
            List<User> userList = [Select id,Name from User where name in :usrName and IsActive=true];
            
            for(ID clientIds : newMap.keySet()){
                Client__c client = newMap.get(clientIds);
                
                                
                    if(client.Client_Manager__c != Null && userList.size() > 0){
                        
                        for(user usr : userList){
                        
                        if(client.Client_Manager__c == usr.Name){
                            client.Client_Manager_Lookup__c = usr.Id;
                        }
                    }
                                        
                }
                else
                    {
                            client.Client_Manager_Lookup__c = Null;
                    }
                
            }
            
        }
        catch(Exception ex){
            System.debug('Exception caught in client insert method :'+ex.getMessage());
        }
    }
    
    public static void ClientUpdate(Map<Id,Client__c> updateMap){
        
        try{
            
            Set<String> usrName = new Set<String>();
        
            for(ID clientIds : updateMap.keySet()){
                            
                Client__c client = updateMap.get(clientIds);
                if(client.Client_Manager__c != Null){
                    usrName.add(client.Client_Manager__c);
                }
            }
            
            List<User> userList = [Select id,Name from User where name in :usrName and IsActive=true];
            
            for(ID clientIds : updateMap.keySet()){
                Client__c client = updateMap.get(clientIds);
                
                                
                    if(client.Client_Manager__c != Null && userList.size() > 0){
                        
                        for(user usr : userList){
                        
                        if(client.Client_Manager__c == usr.Name){
                            client.Client_Manager_Lookup__c = usr.Id;
                        }
                    }
                                        
                }
                else
                    {
                            client.Client_Manager_Lookup__c = Null;
                    }
                
            }
        }
        catch(Exception ex){
            System.debug('Exception caught in client update method :'+ex.getMessage());
        }
    }
    
}


Test Class
----------------

@isTest
private class TestClientTrigger {
    
    @testSetup
    private static void createTestData(){
        
        List<User> usrList = new List<User>();
        
        for(Integer i=0; i<3 ; i++){
            User usr = new User();
            usr.ProfileId = [SELECT Id FROM Profile WHERE Name = 'System Administrator'].Id;
           
            if(i==0){
                usr.FirstName = 'Lakshmi';
                usr.LastName = 'S';
                usr.Email = 'lakshmis@gmail.com';
                usr.Username = 'lakshmis@gmail.com';
                usr.Alias = 'laks';
            }
            else if(i==1){
                usr.FirstName = 'Ajay';
                usr.LastName = 'D';
                usr.Email = 'Ajayd@gmail.com';
                usr.Username = 'Ajayd@gmail.com';
                usr.Alias = 'ajayd';
            }
            else if(i==2){
                usr.FirstName = 'Naresh';
                usr.LastName = 'K';
                usr.Email = 'nareshk@gmail.com;
                usr.Username = 'nareshk@gmail.com';
                usr.Alias = 'naresh';
            }
            
            usr.CompanyName = 'TEST';
            usr.Title = 'title';
            usr.TimeZoneSidKey = 'America/Los_Angeles';
            usr.EmailEncodingKey = 'UTF-8';
            usr.LanguageLocaleKey = 'en_US';
            usr.LocaleSidKey = 'en_US';
            
            usrList.add(usr);
        }
        
        insert usrList;
        
        Account acc = new Account();
        acc.Name = 'Dummy Account';
        insert acc;
        
        Map<Id,Client__c> fsList = new Map<Id,Client__c>();
        
        for(Integer i=0 ; i<3 ; i++){
            Client__c fs = new Client__c();
            fs.Account__c = acc.Id;
            if(i==0){
                fs.Client_Manager__c = 'Lakshmi S';
            }
            else if(i==1){
                fs.Client_Manager__c = 'Ajay D';
            }
            else if(i==2){
                fs.Client_Manager__c = 'Naresh K';
            }
            
            fsList.put(fs.Id,fs);
            
        }
        insert fsList.values();
    }
    
   
    
    @isTest
    private static void updateTest(){
        
        Account acc = [Select id from account];
        
        Client__c fs = [Select id,Client_Manager__c from Client__c limit 1];
        fs.Client_Manager__c = 'Naresh K';
        update fs;
        
    }
    
}

for(Opportunity opp : Trigger.New){
        
        for(User usr : [Select id from user where name =:opp.Manager__c]){

            opp.Manager_Lookup__c = usr.Id;

        }
    }

<apex:pageBlockSectionItem >
                    <Label>Account currently use or Not </Label>
                    <apex:actionRegion >
                        <apex:inputField value="{!Account.Account_currently_use__c}">
                            <apex:actionSupport event="onchange" reRender="desc" />
                        </apex:inputField>
                    </apex:actionRegion>
                    
 </apex:pageBlockSectionItem>
  <apex:outputPanel id="desc" layout="None" >
                <apex:pageBlockSectionItem rendered="{!if(Account.Account_currently_use__c == 'Yes',true,false)}" >
                    Acct currently use(Des)  
                    <apex:inputTextarea cols="50" rows="3" value="{!Account.Acct_currently_use_Des__c}"/>
               </apex:pageBlockSectionItem>
 </apex:outputPanel>

public static void rollupSumUpdate(Map<Id, child1__c> newRecs, Map<Id, child1__c> oldRecs){
   
        try{
            
            Set<String> parentIds = new Set<String>();
            
            for(Id chIds : newRecs.keySet()){
                
                child1__c tr = newRecs.get(chIds);
                
                if(tr.parentId__c != Null){
                    
                    parentIds.add(tr.parentId__c);
                    
                    System.debug('******If block -  Update Method - parentIds : **********'+parentIds);
                }
                else
                {
                    parentIds.add(oldRecs.get(chIds).parentId__c);
                    System.debug('******else block -  Update Method - parentIds : **********'+parentIds);
                }
                
            }
            
            Map<Id,parent__c> mapToUpdate = new Map<Id,parent__c>();
            
            if(parentIds.size() > 0){
                
                Map<Id,parent__c> fsOppMap = new Map<Id,parent__c>([Select Id,Amount__c,Trade_Count__c from parent__c where Id In :parentIds]);
                
                parent__c fsOpp = new parent__c();
                
                List<AggregateResult> ar = [Select parentId__c,Count(Id)tradeCount,Sum(Annual_Recurring_Revenue__c)arrSum,Sum(Non_Recurring_Revenue__c)nrrSum 
                                           from child1__c where parentId__c In :parentIds Group By parentId__c];
                System.debug('--------Aggregate Result : '+ar);
                
                If(ar.size() > 0){
                    
                    for(AggregateResult res : ar){
                        
                        Id fsId = (Id)res.get('parentId__c');
                        fsOpp = fsOppMap.get(fsId);
                        
                        fsOpp.Trade_Count__c = (Integer)res.get('tradeCount');
                        System.debug('---Update Method-----Trade Count : '+fsOpp.Trade_Count__c);
                        
                        Decimal arr = (Decimal)res.get('arrSum');
                        System.debug('----Update Method----ARR : '+arr);
                        
                        Decimal nrr = (Decimal)res.get('nrrSum');
                        System.debug('----Update Method----NRR : '+nrr);
                        
                        fsOpp.Amount__c = arr + nrr ;
                        System.debug('----Update Method----Amount : '+fsOpp.Amount__c);
                        
                        mapToUpdate.put(fsOpp.Id,fsOpp);
                        
                    }
                }
                else
                {
                    for(Id ids : parentIds){
                        
                        fsOpp = new parent__c(id = ids); 
                        
                        fsOpp.Trade_Count__c = Null;
                        System.debug('----Update Method--Else Block--Trade Count : '+fsOpp.Trade_Count__c);
                        
                        fsOpp.Amount__c = 0;
                        System.debug('----Update Method--Else Block--Amount : '+fsOpp.Amount__c);
                        
                        mapToUpdate.put(fsOpp.Id,fsOpp);
                        
                    }
                }
                
            }
            
            Database.SaveResult[] res = Database.update(mapToUpdate.values(), false);
            
            
        }
        catch(Exception ex){
            System.debug('---Exception caught in Rollup Sum Update Method :'+ex.getLineNumber());
        }
        
    }