My requirement was to display picklist values based on user object. In User object Field called ASM__C (Formula Field) and I am retrieving the records based on this field. But I am getting Null value. The values are exist in database for this field.

Please guide me how to get the value...

This is my code-:   
public class ManageAccountAssignmentsController
{

public String selectedAsm{get;set;}
//Public String AsmId{get;set;}
Public List<Account> AsmAssocAccounts{get;set;}
Public boolean MethCal{get;Set;}
Public boolean successMsg{get;Set;}
public Document document {get; set;} 

    public List<SelectOption> getAsmOptions()
    {
      Set<Id> accset = new Set<Id>();
      Id customerRecordTypeId = Schema.SObjectType.Account.RecordTypeInfosByName.get('Customer').RecordTypeId;
      List<Account> acct = New List<Account>();
      Set<id> ArConId = new Set<id>();
      acct = [Select Name, Ownerid, id from Account where RecordTypeId =:customerRecordTypeId];
      for(Account acclst:acct)
      {
        accset.add(acclst.Ownerid);
      }
       List<SelectOption> options = new List<SelectOption>();
       for (User e1:[SELECT Name,id,Area_Controller__c,ASM__c FROM User WHERE id IN:accset])
        {
             ArConId.add(e1.ASM__c); //Getting Null in this Set eventhough value is present in database
             system.debug('ArConId'+ArConId);       
         }
       
       options.add(new selectOption('--None--','--None--'));
        for (User e:[SELECT Name,Id FROM User WHERE id IN:ArConId])
         {
             options.add(new selectOption(e.id,e.Name));
                              
         }
         return options;
    }