键入时自动滚动列表框

Question

我试图为一个ListBox编写VB.Net代码，在其中键入时自动滚动该Listbox。 这样，它将选择并突出显示前几个相似字母的项目； 下面的代码在第一次（即加载表单时）可以正常工作，但此后将停止工作。 任何想法？

Public Class Form1

'AutoScroll Listbox as You Type 
Dim searchChars As String

Private Sub ListBox1_KeyUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles ListBox1.KeyUp
    searchChars += Chr(e.KeyValue)
    ListBox1.SelectedIndex = ListBox1.FindString(searchChars)
End Sub

Private Sub ListBox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles ListBox1.KeyPress
    e.Handled = True
End Sub


Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    ListBox1.Items.Add("Canada")
    ListBox1.Items.Add("USA")
    ListBox1.Items.Add("France")
    ListBox1.Items.Add("Japan")
    ListBox1.Items.Add("Belgium")
    ListBox1.Items.Add("Bulgariaa")
    ListBox1.Items.Add("India")
    ListBox1.Items.Add("Iraq")
    ListBox1.Items.Add("Iran")
    ListBox1.Items.Add("Ireland")
    ListBox1.Items.Add("Malaysia")
    ListBox1.Items.Add("Thailand")
    ListBox1.Items.Add("Bangaladish")
    ListBox1.Items.Add("Italy")
    ListBox1.Items.Add("Republic of Whatever")
End Sub


Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    ListBox2.Items.Add(ListBox1.SelectedItem)
    ListBox1.Focus()
End Sub

末级

Answer 1

您将在此处添加字符：

searchChars += Chr(e.KeyValue)

因此，如果您先按I键，它将找到India ，但是如果再次按I键，则searchChars将包含II那么它将找不到任何内容，因为任何项均以II开头，并且在此之后，您将不会重置附加字符内部searchChars 。

你可以这样做：

Private Sub ListBox1_KeyUp(ByVal sender As Object, ByVal e As KeyEventArgs) _
Handles ListBox1.KeyUp

    sender.SelectedIndex = 
           sender.FindString(Convert.ToChar(e.KeyValue), sender.SelectedIndex)

End Sub

更新：

另一种方法（附加字符）：

Private Sub ListBox1_KeyUp(ByVal sender As Object, ByVal e As KeyEventArgs) _
Handles ListBox1.KeyUp

    Static SearchPattern As String
    SearchPattern &= CStr(Convert.ToChar(e.KeyValue))

    Dim FindIndex As Integer = 
        sender.FindString(SearchPattern)

    If FindIndex = -1 Then
        SearchPattern = CStr(Convert.ToChar(e.KeyValue))
        sender.SelectedIndex = sender.FindString(SearchPattern)

    Else
        sender.SelectedIndex = FindIndex

    End If

End Sub