form1.vb

Mastering VBNet Include Source Code

Option Strict On
Public Class ArraySearchForm
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call

    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub
    Friend WithEvents ListBox1 As System.Windows.Forms.ListBox
    Friend WithEvents bttnPopulate As System.Windows.Forms.Button
    Friend WithEvents bttnSearch As System.Windows.Forms.Button

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.Container

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.ListBox1 = New System.Windows.Forms.ListBox()
        Me.bttnPopulate = New System.Windows.Forms.Button()
        Me.bttnSearch = New System.Windows.Forms.Button()
        Me.SuspendLayout()
        '
        'ListBox1
        '
        Me.ListBox1.Font = New System.Drawing.Font("Verdana", 9.0!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(161, Byte))
        Me.ListBox1.ItemHeight = 14
        Me.ListBox1.Location = New System.Drawing.Point(8, 8)
        Me.ListBox1.Name = "ListBox1"
        Me.ListBox1.Size = New System.Drawing.Size(200, 312)
        Me.ListBox1.TabIndex = 0
        '
        'bttnPopulate
        '
        Me.bttnPopulate.Font = New System.Drawing.Font("Verdana", 9.0!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(161, Byte))
        Me.bttnPopulate.Location = New System.Drawing.Point(216, 8)
        Me.bttnPopulate.Name = "bttnPopulate"
        Me.bttnPopulate.Size = New System.Drawing.Size(120, 40)
        Me.bttnPopulate.TabIndex = 1
        Me.bttnPopulate.Text = "Populate Array"
        '
        'bttnSearch
        '
        Me.bttnSearch.Font = New System.Drawing.Font("Verdana", 9.0!, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, CType(161, Byte))
        Me.bttnSearch.Location = New System.Drawing.Point(216, 64)
        Me.bttnSearch.Name = "bttnSearch"
        Me.bttnSearch.Size = New System.Drawing.Size(120, 40)
        Me.bttnSearch.TabIndex = 2
        Me.bttnSearch.Text = "Search Array"
        '
        'ArraySearchForm
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(346, 325)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.bttnSearch, Me.bttnPopulate, Me.ListBox1})
        Me.Name = "ArraySearchForm"
        Me.Text = "ArraySearch"
        Me.ResumeLayout(False)

    End Sub

#End Region

    Dim words() As String

    Private Sub bttnPopulate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bttnPopulate.Click
        Dim wordLen As Integer
        ' number of words to place on the list
        Dim Nwords As Integer = 999
        ' The words array holds the random words
        ReDim words(Nwords)
        Dim ascChar As Integer

        Dim rnd As System.Random
        rnd = New System.Random()
        Dim rndChar As Char
        Dim thisWord As String
        Dim word, chr As Integer
        Dim T1, T2 As System.DateTime
        T1 = Now
        ' Generate random words and populate list
        For word = 0 To Nwords
            wordLen = CInt(rnd.Next(3, 15))
            thisWord = ""
            For chr = 0 To wordLen
                rndChar = ChrW(65 + rnd.Next(0, 25))
                thisWord = thisWord & rndChar
            Next
            words(word) = thisWord
            'ListBox1.Items.Add(thisWord)
        Next
        ' show how long it took to generate words
        T2 = Now
        MsgBox("It took " & ((T2.Ticks - T1.Ticks) / 10000).ToString & " msecs to create array")

        ' now sort the list
        T1 = Now
        ListBox1.Items.Clear()
        System.Array.Sort(words)
        ' show how long it took to sort the array with the words
        T2 = Now
        MsgBox("It took " & ((T2.Ticks - T1.Ticks) / 10000).ToString & " msecs to sort array")
        T1 = Now
        ' now add the words to the ListBox control
        For word = 0 To Nwords
            ListBox1.Items.Add(words(word))
        Next
        ' and show how long it took to populate the control
        T2 = Now
        MsgBox("It took " & ((T2.Ticks - T1.Ticks) / 10000).ToString & " msecs to refresh the List Box")
    End Sub

    Private Sub bttnSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles bttnSearch.Click
        Dim srchWord As String      ' the word to search for
        Dim wordIndex As Integer    ' the index of the word in the list (if found)
        srchWord = InputBox("Enter word to search for")
        ' perform a binary search to locate the word, because the list is sorted
        wordIndex = System.Array.BinarySearch(words, srchWord)
        Console.WriteLine(wordIndex)

        If wordIndex >= 0 Then  ' Zero or positive value indicates an exact match
            MsgBox("Words(" & wordIndex.ToString & ") = " & words(wordIndex), , "EXACT MATCH")
            ListBox1.TopIndex = wordIndex
            ListBox1.SelectedIndex = wordIndex
        Else
            ' a negative value indicates a near match (the first item after the location
            ' of the item we search for, if it were in the list
            MsgBox("Words(" & (-wordIndex - 1).ToString & ") = " & words(-wordIndex - 1), , "NEAR MATCH")
            ListBox1.TopIndex = -wordIndex - 1
            ListBox1.SelectedIndex = -wordIndex - 1
        End If
    End Sub
End Class