ComboBox 无法从 KeyValuePair 转换为 Integer

Question

我收到一个 DataBinding 错误，其中我的 ComboBox 绑定到 KeyValuePair 列表并且存储到 DataBase 的值是一个整数。

我该如何转换它？

到目前为止，这是我的代码：

Private Sub SetupeCombo()
     Dim comboSource = New List(Of KeyValuePair(Of Integer, String))

     For Each o In _List
          comboSource.Add(New KeyValuePair(Of Integer,String)(o.ID, o.Details))
     Next

     comboBox1.DisplayMember = NameOf(Table.Details)
     comboBox1.ValueMember =  NameOf(Table.ID)
     comboBox1.DataSource = New BindingSource(comboSource, Nothing)
End Sub

Public Sub BindComboBox()
     Dim comboBoxBindings = comboBox1.DataBindings.Add(NameOf(ComboBox.SelectedValue), dataSource, NameOf(dataSource.ID), True, DataSourceUpdateMode.OnPropertyChanged, String.Empty)        
     AddHandler comboBoxBindings.BindingComplete, AddressOf comboBoxBindings _BindingComplete
End Sub

Private Sub comboBoxBindings_BindingComplete(ByVal sender As Object, ByVal e As BindingCompleteEventArgs)
      If e.BindingCompleteState <> BindingCompleteState.Success Then MessageBox.Show("Test: " & e.ErrorText)
End Sub

错误

Test: Value[1, TestValue] cannot be converted to a type 'ID'

Answer 1

不应该是

comboBox1.DisplayMember = "Value"
comboBox1.ValueMember =  "Key"

相反，当您添加键值对时？

Answer 2

最终使用自定义 ComboBox Class 解决了问题。在我的 DTO 中，我创建了一个 String 属性，其中 returns 是 ID（整数）和描述（字符串）的组合值。

使用这个属性我能够设置 DisplayMember 并且 ValueMember 被设置为 DataBinding 也使用的 ID 字段。所以最后不需要铸造。

示例：

Public Class ComboBox
    Public Property Details As String
    Public Property ID As Integer
    Public ReadOnly Property Display() As String
        Get 
            Return $"{ID}: {Details}"
        End Get
    End Property
End Class

并且在修改我的SetupCombo方法之后。

Private Sub SetupeCombo()
     Dim comboSource = _list.Select(Function(x) New CombBox With{
                                  .ID = x.ID, 
                                  .Details = x.Details})
                            .ToList()   

     comboBox1.DisplayMember = NameOf(ComboBox.Display)
     comboBox1.ValueMember =  NameOf(ComboBox.ID)
     comboBox1.DataSource = comboSource
End Sub

最后是我的 DataBinding

Public Sub BindComboBox()
     Dim comboBoxBindings = comboBox1.DataBindings.Add(NameOf(ComboBox.SelectedValue), dataSource, NameOf(ComboBox.ID), True, DataSourceUpdateMode.OnPropertyChanged, String.Empty)        
     AddHandler comboBoxBindings.BindingComplete, AddressOf comboBoxBindings _BindingComplete
End Sub

ComboBox 无法从 KeyValuePair 转换为 Integer

ComboBox cannot convert from KeyValuePair to Integer

vb.net

data-binding

winforms

keyvaluepair