Asp.net 使用 entity framework 到运行 join 语句并在 GridView 中显示

Question

Schedule table:

ScheduleId(PK), AirplaneId(FK), OriginId(FK), Duration-String

Airplane table:

AirplaneId(PK), PlaneCode-String

Origin table:

OriginId(PK), OriginName-String

我想显示如下内容：

ScheduleId | PlaneCode | OriginName | Duration

Schedule.vb

Public Class Schedule
Public Property ID As Int32
Public Property Duration As String

'Foreign key of airplane_Id
Public Overridable Property Airplane As Airplane
'Foreign key of origin_Id
Public Overridable Property Origin As Origin  
End Class

Airplane.vb

Public Class Airplane
Public Property ID As Int32
Public Property PlaneCode As String
End Class

Origin.vb

Public Class Origin
Public Property ID As Int32
Public Property OriginName As String
End Class

我的网格视图：

<asp:GridView ID="gvSearchFlight" runat="server" ItemType="CIM.Schedule" SelectMethod="gvSearchFlight_GetData" AutoGenerateColumns="false" GridLines="None">

GridView 的 SelectMethod:

Dim dbContext As New ApplicationDbContext

    Public Function gvSearchFlight_GetData() As IQueryable(Of Schedule)
    Dim schedules = (From sche In dbContext.Schedule
                     Join air In dbContext.Airplane
                    On sche.Airplane.ID Equals air.ID).ToList()
    Return schedules
End Function

但是我一直收到这个错误：

Unable to cast object of type 'System.Collections.Generic.List1[VB$AnonymousType_112[CIM.Schedule,CIM.Airplane]]' to type 'System.Linq.IQueryable`1[CIM.Schedule]'

编辑：我真的不知道如何写"Select New"语句..

Public Class ScheduleInformation
Public Property Schedule As Schedule
Public Property Airplane As Airplane
Public Property Origin As Origin
End Class

    Public Function gvSearchFlight_GetData() As IQueryable(Of ScheduleInformation)
    Dim schedules = (From sche In dbContext.Schedule
                     Join air In dbContext.Airplane On sche.Airplane.ID Equals air.ID
                     Join ori In dbContext.Origin On sche.Origin.ID Equals ori.ID
                     Select New ScheduleInformation())
    Return schedules
End Function

Answer 1

这是我解决问题的方法。

ScheduleInformation.vb

Public Class ScheduleInformation
  Public Property Schedule As Schedule
  Public Property Airplane As Airplane
  Public Property Origin As Origin
End Class

GridView 的 SelectMethod

'GridView's SelectMethod to get data
Public Function gvSearchFlight_GetData() As IQueryable(Of ScheduleInformation)
    Dim schedules = (From sche In dbContext.Schedule
                 Join air In dbContext.Airplane On sche.Airplane.ID Equals air.ID
                 Join ori In dbContext.Origin On sche.Origin.ID Equals ori.ID
                 Select New ScheduleInformation With {.Schedule = sche, .Airplane = air, .Origin = ori})
    Return schedules
End Function

然后，在我的标签中，我是这样写的：

<asp:GridView ID="gvSearchFlight" runat="server" ItemType="CIM.ScheduleInformation" SelectMethod="gvSearchFlight_GetData" AutoGenerateColumns="false">...

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