无法将'ItemStore.Item'类型的对象强制转换为'System.Collections.IEnumerable'

Question

在视图中显示项目列表时出现问题。无法将它从ItemStore.Item转换为IEnumerable，我还将“@Method List（Of ItemStore.Item）”添加到list.vbhtml并且它无法显示传入字典的项目是类型' Item Store.Item'，但是这个字典需要一个'System.Collections.Generic.List`1 [Item Store.Item]'类型的模型项。

的 的 **** CatalogueController 的 * ** * ** * ** *

    Function About() As ActionResult
        Return View()
    End Function

    Function Index() As String
        Return "Index"
    End Function

    Function List(search As String) As ActionResult
        Dim model As New SQLItemModel
        Dim items = model.SelectById(search)
        Return View(items)

    End Function

的 的 ** * ** * List.vbhtml 的 * ** * ** * ****

    The search text is @ViewBag.Message

    @For Each item In Model
        @item.ID

的 的 ** * ** * *** SQLItemModel.vb 的 * ** * ** * ** * * < /强>

Private connectionString As String = My.Settings.sqlconnection

Public Function SelectAll() As ICollection(Of Item)
    Dim items As New List(Of Item)
    Using connection As New SqlConnection(connectionString)
        connection.Open()
        Dim cmd As New SqlCommand("select * from item", connection)
        Dim reader As SqlDataReader = cmd.ExecuteReader()
        While reader.Read()
            items.Add(GetItem(reader))
        End While
    End Using
    Return items
End Function

Public Function SelectById(ItemID As Integer) As Item
    Dim item As Item = Nothing
    Using connection As New SqlConnection(connectionString)
        connection.Open()
        Dim cmd As New SqlCommand()
        cmd.CommandText = "select * from Tbl_Items where ID = @ID"
        cmd.Connection = connection
        cmd.Parameters.Add(New SqlParameter("ID", ItemID))
        Dim reader As IDataReader = cmd.ExecuteReader()
        If reader.Read() Then
            Item = GetItem(reader)
        End If
    End Using
    Return Item
End Function

Private Function GetItem(reader As SqlDataReader) As Item

    Dim ID = reader("ID")
    Dim ProductCode = reader("ProductCode")
    Dim Brand = reader("Brand")
    Dim Description = reader("Description")
    Dim Colour = reader("Colour")
    Dim Finish = reader("Finish")
    Dim Type = reader("Type")
    Dim Size = reader("Size")
    Dim Unit = reader("Unit")

    Return New Item(ID, ProductCode, Brand, Description, Colour, Finish, Type, Size, Unit)
End Function

Answer 1

SelectById只返回一个Item（而SelectAll会返回Item s的集合，但您的列表视图需要一个集合。

一个简单的解决方法是将单个项目包装在一个数组中：

Function List(search As String) As ActionResult
    Dim model As New SQLItemModel
    Dim items = model.SelectById(search)
    Return View({items})
End Function