Question

我使用下面的函数返回一个SelectList。我需要在Descr上使用自定义格式，但将Key.ToString（）替换为Key.ToString（“DD / MM / YY”）会导致错误“Method'System.String ToString（System.String）'没有支持的翻译到SQL。“我如何在Descr上使用自定义日期格式？

    Public Function ReturnDates(ByVal Param_Pesq_Cod As Integer) As SelectList
        Dim Qry = From E In DB.Execs _
        Where E.Pesq_Cod = Param_Pesq_Cod _
        Group E By Key = E.DataHora.Date _
        Into Group Order By Key Select New With {.Descr = Key.ToString(), .Val = Key}

        Return New SelectList(Qry, "Val", "Descr")
    End Function

Answer 1

如果将转换放在LINQ to SQL查询中，它将尝试从中创建SQL查询。首先获得结果，将其实现为日期列表，然后使用LINQ to Objects进行转换。

我认为它是这样的：

Public Function ReturnDates(ByVal Param_Pesq_Cod As Integer) As SelectList
  Dim Qry = From E In DB.Execs _
  Where E.Pesq_Cod = Param_Pesq_Cod _
  Group E By Key = E.DataHora.Date _
  Into Group Order By Key Select Key

  Dim List = _
    Qry.ToList() _
    .Select(Function(d) New With {.Descr = d.ToString(), .Val = d})

  Return New SelectList(List, "Val", "Descr")
End Function

从Linq到SQL查询的自定义日期格式

1 个答案: