form1.vb

编程之道VB.NETt程序设计入门-589M.zip

Public Class Form1
    Inherits System.Windows.Forms.Form

#Region " Windows 窗体设计器生成的代码 "

    Public Sub New()
        MyBase.New()

        '该调用是 Windows 窗体设计器所必需的。
        InitializeComponent()

        '在 InitializeComponent() 调用之后添加任何初始化

    End Sub

    '窗体重写处置以清理组件列表。
    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

    'Windows 窗体设计器所必需的
    Private components As System.ComponentModel.IContainer

    '注意：以下过程是 Windows 窗体设计器所必需的
    '可以使用 Windows 窗体设计器修改此过程。
    '不要使用代码编辑器修改它。
    Friend WithEvents btnRight As System.Windows.Forms.Button
    Friend WithEvents btnWrong As System.Windows.Forms.Button
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        Me.btnRight = New System.Windows.Forms.Button()
        Me.btnWrong = New System.Windows.Forms.Button()
        Me.SuspendLayout()
        '
        'btnRight
        '
        Me.btnRight.Location = New System.Drawing.Point(48, 56)
        Me.btnRight.Name = "btnRight"
        Me.btnRight.Size = New System.Drawing.Size(128, 32)
        Me.btnRight.TabIndex = 0
        Me.btnRight.Text = "使用BookHashTable"
        '
        'btnWrong
        '
        Me.btnWrong.Location = New System.Drawing.Point(48, 144)
        Me.btnWrong.Name = "btnWrong"
        Me.btnWrong.Size = New System.Drawing.Size(128, 32)
        Me.btnWrong.TabIndex = 0
        Me.btnWrong.Text = "使用HashTable"
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(6, 14)
        Me.ClientSize = New System.Drawing.Size(292, 266)
        Me.Controls.AddRange(New System.Windows.Forms.Control() {Me.btnRight, Me.btnWrong})
        Me.Name = "Form1"
        Me.Text = "Form1"
        Me.ResumeLayout(False)

    End Sub

#End Region

    Private Sub btnRight_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRight.Click
        Dim b As New Book()
        b.Name = "倚天屠龙记"
        b.Price = 20
        b.Author = "金庸"

        Dim bookHt As BookHashTable
        bookHt = New BookHashTable()
        Try
            '在类型安全的哈希表中放入和取出类型正确的数据
            '可以工作的很好，而且不需要强制转型
            bookHt.Add(b.Name, b)
            b = bookHt.Item(b.Name)
            MessageBox.Show(bookHt.Item(b.Name).DisplayBook)

            '由于采用了类型安全的哈希表
            '以下的语句没办法通过编译()
            '
            'ht.Add("aString", "一个字符串")
            'MessageBox.Show(ht.Item("aString"))
        Catch ex As Exception
            MessageBox.Show("出现异常：" & ex.Message)
        End Try
    End Sub

    Private Sub btnWrong_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnWrong.Click
        Dim b As New Book()
        b.Name = "倚天屠龙记"
        b.Price = 20
        b.Author = "金庸"

        Dim ht As Hashtable
        ht = New Hashtable()
        Try
            '在类型不安全的哈希表中放入和取出Book类型的数据
            '可以工作
            ht.Add(b.Name, b)
            b = ht.Item(b.Name)
            MessageBox.Show(b.DisplayBook)

            '在同一个类型不安全的哈希表中放入和取出String类型的数据
            '也可以工作
            ht.Add("aString", "一个字符串")
            MessageBox.Show(ht.Item("aString"))

            '如果有人不知道这是一个String类型的数据，
            '而把它当Book型来用，就会在运行时出错
            b = ht.Item("aString")
            MessageBox.Show(b.DisplayBook)
        Catch ex As Exception
            MessageBox.Show("出现异常：" & ex.Message)
        End Try
    End Sub
End Class