Question

我的VB表单中有1个文本框和1个列表框。

我想检查重复的项目，与textbox.text1和listbox.list项目进行比较。

如果textbox.text1值为'3333'且listbox.list多值为'1111''2222''3333''4444'

那么如何实现像重复检查例程一样？

因此，如果重复检测与当前text1值进行比较，则与列表框中的一个进行比较

值是if detect，想要弹出消息框

提前致谢

Answer 1

假设您要在ListBox中插入字符串，您可以这样做：

Private Sub button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
    Dim x As String
    For Each x In ListBox1.Items
        If (x = TextBox1.Text) Then
            MessageBox.Show("Error")
            Return
        End If
    Next
    ListBox1.Items.Add(TextBox1.Text)
End Sub

如果它是具有名为Value的属性的另一种类型的对象，那么您需要进行一些小改动：

Private Sub button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
    Dim x As Foo
    For Each x In ListBox1.Items
        If (x.Value = TextBox1.Text) Then
            MessageBox.Show("Error")
            Return
        End If
    Next
    ListBox1.Items.Add(TextBox1.Text)
End Sub

Answer 2

假设ListBox包含字符串，您可以使用Contains集合的Items方法检查匹配项。示例（制作一个名为'_TheListBox'的ListBox表单，一个名为'_TextBox'的TextBox和一个名为'_theLabel'的Label表单：

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    _theListBox.Items.AddRange(New String() {"aaaa", "bbbb", "cccc", "dddd"})
End Sub

Private Sub _theTextBox_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles _theTextBox.TextChanged
    If ListBoxContainsItem(_theListBox, _theTextBox.Text) Then
        _theLabel.Text = "It's a match"
    Else
        _theLabel.Text = ""
    End If
End Sub

Private Function ListBoxContainsItem(ByVal lb As ListBox, ByVal text As String) As Boolean
    ' check if the string is present in the list '
    Return lb.Items.Contains(text)
End Function

visual basic List.box问题

2 个答案: