vb.net - 从组合框中获取所选项目

Question

我有一个包含来自 DataTable 的项目的组合框，ff 在表单加载时执行:

dbConnection = New SqlCeConnection("Data Source=Journal.sdf")
dbDataAdapter = New SqlCeDataAdapter("SELECT * FROM setting_unit", dbConnection)
dbDataAdapter.Fill(dbTable)
cbxSettingsUnit.DataSource = New BindingSource(dbTable, Nothing)
cbxSettingsUnit.DisplayMember = "name"
cbxSettingsUnit.ValueMember = "name"

组合框发生变化时的方法:

Private Sub cbxSettingsUnit_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cbxSettingsUnit.SelectedIndexChanged
   tempString = cbxSettingsBusinessUnit.Items(cbxSettingsBusinessUnit.SelectedItem).ToString
   MessageBox.Show(tempString)
End Sub

行有错误:

tempString = cbxSettingsBusinessUnit.Items(cbxSettingsBusinessUnit.SelectedItem).ToString

如何从组合框中获取所选项目？

Answer 1

大多数.net “listing-controls” 拥有DataSource 属性搜索IListSource 的实现.因此，如果您将 DataTable 设置为数据源，您实际上是将 DataTable.DefaultView 设置为数据源。

Me.ComboBox1.DataSource = myDataTabele

等于

Me.ComboBox1.DataSource = myDataTabele.DefaultView

所以现在你有一个包含 DataRowView 类型项目的 ComboBox。

Dim selectedRowView As DataRowView = DirectCast(Me.ComboBox1.SelectedItem, DataRowView)
Dim selectedDisplayMemberValue As String = Me.ComboBox1.SelectedText
Dim selectValueMemberValue As Object = Me.ComboBox1.SelectedValue

你应该这样做:

Private Sub cbxSettingsUnit_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cbxSettingsUnit.SelectedIndexChanged
    Dim item As DataRowView = TryCast(Me.cbxSettingsUnit.SelectedItem, DataRowView)
    If (Not item Is Nothing) Then
        With item.Row
            'You have now access to the row of your table.
            Dim columnValue1 As String = .Item("MyColumnName1").ToString()
            Dim columnValue2 As String = .Item("MyColumnName2").ToString()
        End With
    End If
End Sub

那么为什么会出现错误？是的，您正在尝试将 DataRowView 转换为 Integer。

'                                                                      |
tempString = cbxSettingsBusinessUnit.Items(cbxSettingsBusinessUnit.SelectedItem).ToString