不能隐式转换类型'System.DateTime？'到'int？' C＃Linq

Question

代码：它突出了我可以告诉Linq找到shipto列并将另一个表上的datetimestamp更新一段时间的最底部，并告诉我不能隐式地将类型'System 。约会时间？'到'int？'而且我不确定如何继续......

var TestingLinq = (from a in db.shp_master 
        join b in db.shp_status on a.serialnbr equals b.serialnbr into b_join 
        from b in b_join.DefaultIfEmpty() 
        where 
           a.shipto == "1022a" && 
           a.status == "s" && 
           b.status == "s" && 
           a.shpreq == 0 
        group new {a, b} by new { 
           a.serialnbr, 
           a.trailer, 
           a.shipto 
        } into g 
        orderby 
           g.Key.serialnbr 
        select new RecieveTruck { 
           SerialNumber = g.Key.serialnbr, 
           TrailerNumber = (g.Key.trailer ?? "N/A"), 
           Shipped = g.Min(p => p.b.datetimestamp), 
           ETA = 
           g.Key.shipto == "1026" ? (System.DateTime?)Convert.ToDateTime(g.Min(p => p.b.datetimestamp)).AddMinutes(180) : 
           g.Key.shipto == "2020" ? (System.DateTime?)Convert.ToDateTime(g.Min(p => p.b.datetimestamp)).AddMinutes(195) : 
           g.Key.shipto == "2017" ? (System.DateTime?)Convert.ToDateTime(g.Min(p => p.b.datetimestamp)).AddMinutes(180) : 
           g.Key.shipto == "nor" ? (System.DateTime?)Convert.ToDateTime(g.Min(p => p.b.datetimestamp)).AddMinutes(180) : null 
        }); 
    return View(TestingLinq); 

让我在标题中错误.... 我想这个SQL查询转换为LINQ的：

SELECT a.serialnbr, ISNULL(a.trailer, 'N/A') AS 'trailer', MIN(b.datetimestamp) AS 'datetimestamp', 
      CASE WHEN a.shipto = '1026' THEN DATEADD(mi, 180, MIN(b.datetimestamp)) 
        WHEN a.shipto = '2020' THEN DATEADD(mi, 195, MIN(b.datetimestamp)) 
        WHEN a.shipto = '2017' THEN DATEADD(mi, 180, MIN(b.datetimestamp)) 
        WHEN a.shipto = 'nor' THEN DATEADD(mi, 180, MIN(b.datetimestamp)) 
        ELSE NULL END AS 'eta' 
      FROM shp_master AS a LEFT OUTER JOIN shp_status AS b ON a.serialnbr = b.serialnbr 
      WHERE a.shipto = '1022a' AND a.status = 's' AND b.status = 's' AND a.shpreq = 0 
      GROUP BY a.serialnbr, a.trailer, shipto 
      ORDER BY a.serialnbr  

Answer 1

在你发表评论，您指定RecieveTruck.ETA是int?，但你这样做

ETA = g.Key.shipto == "1026" ? (System.DateTime?)Convert.ToDateTime(g.Min(p => p.b.datetimestamp)).AddMinutes(180) : 
     g.Key.shipto == "2020" ? (System.DateTime?)Convert.ToDateTime(g.Min(p => p.b.datetimestamp)).AddMinutes(195) : 
     g.Key.shipto == "2017" ? (System.DateTime?)Convert.ToDateTime(g.Min(p => p.b.datetimestamp)).AddMinutes(180) : 
     g.Key.shipto == "nor" ? (System.DateTime?)Convert.ToDateTime(g.Min(p => p.b.datetimestamp)).AddMinutes(180) : null 

分配它，这将解决一个DateTime?。你需要选择一个或另一个。它看起来像你在寻找ETA是一个DateTime?，但是，所以我只是改变该属性类型，你应该很好去。