clear listbox items except for searched items vb.net

Question

Hi,

I am using the below code to find all the items in a listbox using vb.net 2005. But how can remove the non searched items from the listbox after searching?

EDIT : I included the entire code

 Imports System.IO

Public Class Form1
    Public Sub New()

         InitializeComponent()
        ListBox1.SelectionMode = SelectionMode.MultiExtended


    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        Dim reader As StreamReader = New StreamReader("input.txt")
        Try
            Me.ListBox1.Items.Clear()
            Do
                Me.ListBox1.Items.Add(reader.ReadLine)
            Loop Until reader.Peek = -1

        Catch
            Me.ListBox1.Items.Add("File is empty")

        Finally
            reader.Close()
        End Try
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        ListBox1.BeginUpdate()
        ListBox1.SelectedIndices.Clear()
        If TextBox1.Text.Length > 0 Then
            For index As Integer = 0 To ListBox1.Items.Count - 1
                Dim item As String = ListBox1.Items(index).ToString()

                If item.IndexOf(TextBox1.Text, StringComparison.CurrentCultureIgnoreCase) >= 0 Then

                    ListBox1.SelectedIndices.Add(index)
                End If
            Next
        End If
        ListBox1.EndUpdate()
    End Sub

    Private Sub ListBox1_DragEnter(ByVal sender As Object, ByVal e As  _
 System.Windows.Forms.DragEventArgs) Handles ListBox1.DragEnter
        If e.Data.GetDataPresent(DataFormats.FileDrop) Then
            e.Effect = DragDropEffects.All
        End If
    End Sub

    Private Sub ListBox1_DragDrop(ByVal sender As Object, ByVal e As  _
    System.Windows.Forms.DragEventArgs) Handles ListBox1.DragDrop
        If e.Data.GetDataPresent(DataFormats.FileDrop) Then
            Dim MyFiles() As String

            Me.ListBox1.Items.Clear()

            MyFiles = e.Data.GetData(DataFormats.FileDrop)
            Using sr As StreamReader = New StreamReader(MyFiles(0))
                Dim line As String

                Do
                    line = sr.ReadLine()

                    ListBox1.Items.Add(line)
                Loop Until line Is Nothing

            End Using

        End If
    End Sub
End Class

Answer 1

Create a List<string> with all your items in it and search that list, then only add the results of the search to your listbox.

Off course you'd have all items in your listbox to start with, but then also in the List. Then clear your listbox and search the list for the item entered in the textbox. now you can add the search results to your listbox.

Answer 2

It sounds to me like you want something like this:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    ListBox1.BeginUpdate()

    Try
        ' keep track of the "non-searched items" '
        Dim indicesToRemove As New List(Of Integer)

        ListBox1.SelectedIndices.Clear()
        If TextBox1.Text.Length > 0 Then
            For index As Integer = 0 To ListBox1.Items.Count - 1
                Dim item As String = ListBox1.Items(index).ToString()

                If item.IndexOf(TextBox1.Text, StringComparison.CurrentCultureIgnoreCase) >= 0 Then
                    ListBox1.SelectedIndices.Add(index)
                Else
                    ' this item was not searched for; we will remove it '
                    indicesToRemove.Add(index)
                End If
            Next

            ' go backwards to avoid problems with indices being shifted '
            For i As Integer = indicesToRemove.Count - 1 To 0 Step -1
                Dim indexToRemove As Integer = indicesToRemove(i)
                ListBox1.Items.RemoveAt(indexToRemove)
            Next
        End If
    Finally
        ListBox1.EndUpdate()
    End Try
End Sub

Notice I also put the call to ListBox1.EndUpdate() in a Finally block. In my experience this is a good practice, as it ensures your control will return to a normal state even in the event of an exception (which you can still handle however you like).