查询列表

Question

我有以下嵌套的ViewModels：

Public Class ContentViewModel 
    Public Property CONTENTID As Integer 
    Public Property IMAGETOCONTENT() As IEnumerable(Of ImageToContentViewModel) 
End Class 

Public Class ImageToContentViewModel 
    Public Property IMAGETOCONTENTID As Integer 
    Public Property IMAGE As ImageViewModel 
End Class 

Public Class ImageViewModel 
    Public Property IMAGEID As Integer 
    Public Property TITLE As String 
End Class 

我想查询嵌套的ViewModels：

Function Test() As ContentViewModel 
    Dim dataObject = (From a In db.CMS_CONTENT.OfType(Of CMS_EVENT)() 
       Where a.CONTENTID = contentId AndAlso a.DELETED = 0 
       Select New ContentViewModel With { 
        .CONTENTID = a.CONTENTID,       
        .IMAGETOCONTENT = (From b In db.CMS_IMAGES_TO_CONTENT 
         Where b.CONTENTID = a.CONTENTID 
         Select New ImageToContentViewModel With { 
          .IMAGETOCONTENTID = b.IMAGETOCONTENTID, 
          .IMAGE = (From c In db.CMS_IMAGES 
            Where c.IMAGEID = b.IMAGEID And c.DELETED = False 
            Select New ImageViewModel With { 
             .IMAGEID = c.IMAGEID, 
             .TITLE = c.TITLE 
            }) 
         }) 
       }) 

    Return dataObject 
End Function 

我的问题是，我不能返回人口viewmodel，因为我总是得到错误：

类型“System.Data.Objects.ObjectQuery`1 [MvcApp.ContentViewModel]”的对象无法转换为“MvcApp.ContentViewModel”

Answer 1

您的功能主体创建了IQueryable的ContentViewModel（实现为System.Data.Objects.ObjectQuery`1[MvcApp.ContentViewModel]），因为那是Select返回的值。

您要么使用FirstOrDefault()，要么将返回类型更改为IQueryable（的ContentViewModel）。