Question

我试图通过添加天来选择可以为空的日期时间。

正如

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

如果datetime有值，我想通过选择上面的查询来添加1天。

如果datetime没有值，我想通过选择上面的查询来设置可为空的日期时间。

但是，如果我尝试上面的代码，我会得到错误（请检查底部是否有错误）

所有查询：

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();

错误：

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.

问题：

如何在选择部分中选择添加日期时间或空日期时间？

任何帮助将不胜感激。

感谢。

Answer 1

如果您使用的是EF 6，则可以使用DbFunctions

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 ? Dbfunctions.AddDays(x.VISIT_DATE.value, 1) : (DateTime?)null) // Problem in this part

  }).ToList();

如何通过在linq查询中选择来添加日期到日期时间

1 个答案: