hi

rathore_1987

very simple trigger code to Update Account Custom FIeld when New Contact is Created 

"

trigger AfterCreateOrUpdateContact on Contact (after insert,after update) {
    if(ConfigUtilController.getAfterCreateOrUpdateContact()){     
         List < Id > contactIds = new List < Id >();
         List < Id > contactAcIds = new List < Id >();
         
         for ( Contact  c : Trigger.New ) {
         
             contactIds.add( c.Id );
             contactAcIds.add( c.AccountID );
         
         }
         
         List < Account >  accountsOfContacts  = [select a.ID,
                                  a.Name,
                                  a.Default_Contact__C,
                                  a.Account_Key__c,
                                  a.AccountNumber
                                  from Account a
                                  where a.Id in : contactAcIds];
                                  
         
         Map < Id ,Account > accmap = new Map < Id , Account >();
         
         for ( Account  a : accountsOfContacts   ) {
         
             accmap.put( a.Id, a);
         }
         
         List < Account > accToUpdate = new List < Account >();
             
         for(Contact c: Trigger.New) {
            Account ac = accmap.get( c.AccountID );
                
            if ( ac == null ) {
                
                continue;
            }
            If (c.Default__c == true){
                
                 ac.Default_Contact__C = c.ID;
                 accToUpdate.add( ac );
                 
            }else if ( ac.Default_Contact__C == null  ) {
            
                ac.Default_Contact__C = c.ID;
                accToUpdate.add( ac );
            }
         }
         
         upsert accToUpdate;       
    }
}

"

hope this help for you

regards,

Hitesh N. Patel