how to add days to datetime by selecting in linq query

I'm trying to select nullable datetime by adding days.

As instance

COMPLETE_TIME = (x.VISIT_DATE.HasValue ? x.VISIT_DATE.Value.AddDays(1) : (DateTime?)null)

If datetime has value i want to add 1 days by selecting query as above.

If datetime does not have value i want to set nullable datetime by selecting query as above.

However if i try above code i get Error (please check bottom side for error)

All Query:

var result=

 (from s in context.SURVEYs
 join x in context.SURVEY_X on s.SURVEY_ID equals x.SURVEY_ID
 join sas in context.SURVEY_ANSWER_SELECTION on s.SURVEY_ID equals sas.SURVEY_ID 
 join o in context.REP_OPTION on sas.OPTION_ID equals o.OPTION_ID

    from PCO in context.REP_PARENT_CHILD_OPTIONS.Where(w => w.CHILD_OPTION_ID == sas.OPTION_ID).DefaultIfEmpty()

    where
    (s.SURVEY_ID == 5 || s.PARENT_SURVEY_ID == 5) && 
    o.SUGGESTION != null &&
    PCO.PARENT_OPTION_ID == null
      select new
      {
        SUGGESTION = o.SUGGESTION,
        DISPLAY_ORDER = "0",
        SUGGESTION_TYPE = o.SUGGESTION_TYPE,
        o.EXAMPLE_IMAGE_ID,

COMPLETE_TIME = (x.VISIT_DATE.HasValue ? x.VISIT_DATE.Value.AddDays(1) : (DateTime?)null) // Problem in this part

      }).ToList();

Error:

An exception of type 'System.NotSupportedException' occurred in EntityFramework.SqlServer.dll but was not handled in user code

Additional information: LINQ to Entities does not recognize the method 'System.DateTime AddDays(Double)' method, and this method cannot be translated into a store expression.

Question:

How can i select added datetime or null datetime in select part ?

Any help will be appreciated.

Thanks.