Question

我有后期绑定这个问题：我正在创建一个购物清单应用程序。我有一个名为Item的班级，用于存储购物清单上商品的name，price，quantity和description。

我有一个名为ListCollection的模块，它定义了Collection个Item个对象。我创建了一个Edit表单，它会自动显示当前选中的ListCollection项属性，但每当我尝试填充文本框时，它都会告诉我Option Strict不允许后期绑定。

我可以采用简单的路线并禁用Option Strict，但我更愿意弄清问题是什么，所以我知道以供将来参考。

我将在此处粘贴相关代码。（后期绑定错误在EditItem.vb。）

Item.vb代码：

' Member variables:
Private strName As String

' Constructor
Public Sub New()
    strName = ""

' Name property procedure
Public Property Name() As String
    Get
        Return strName
    End Get
    Set(ByVal value As String)
        strName = value
    End Set
End Property

ListCollection.vb代码：

' Create public variables.
Public g_selectedItem As Integer ' Stores the currently selected collection item.

' Create a collection to hold the information for each entry.
Public listCollection As New Collection

' Create a function to simplify adding an item to the collection.
Public Sub AddName(ByVal name As Item)
    Try
        listCollection.Add(name, name.Name)
    Catch ex As Exception
        MessageBox.Show(ex.Message)
    End Try
End Sub

EditItem.vb代码：

Private Sub EditItem_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    ' Set the fields to the values of the currently selected ListCollection item.
    txtName.Text = ListCollection.listCollection(g_selectedItem).Name.Get ' THIS LINE HAS THE ERROR!

我尝试声明String变量并为其分配Item属性，我也尝试直接从List项中获取值（不使用{{1}功能），这些都没有区别。

如何解决此问题？

Answer 1

您必须将项目从“对象”转换为您的类型（“EditItem”）。

http://www.codeproject.com/KB/dotnet/CheatSheetCastingNET.aspx

编辑：

Private Sub EditItem_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    ' getting the selected item
    Dim selectedItem As Object = ListCollection.listCollection(g_selectedItem)

    ' casting the selected item to required type
    Dim editItem As EditItem = CType(selectedItem, EditItem)

    ' setting value to the textbox
    txtName.Text = editItem.Name

我在VB.NET中没有编写任何代码多年，我希望它没事。

后期绑定和Option Strict

1 个答案: