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1、实例 53：获得拨号网络项目实例说明在本实例中，我们将制作一个能够取得本地计算机上的拨号网络的项目的应用程序。 程序运行结果如图 53-1 所示。图 53-1 运行结果技术要点读取注册表内容 添加到列表框实现过程新建项目打开 Visual Studio.NET，选择“新建项目” ，在项目类型窗口中选择“Visual Basic 项 目” ，在模板窗口中选择“Windows 应用程序” ，在名称域中输入“GetDialList” ，然后选 择保存路径。单击“确认” 。添加控件和设置属性向窗体上添加一个 ListBox 控件。将窗体的 Text 属性改为“获得拨号网络项目”，其余 属性都保持默认。
2、添加代码Private Declare Function RegOpenKey Lib “advapi32.dll“ Alias “RegOpenKeyA“(ByVal hKey As Integer, ByVal lpSubKey As String, ByRef phkResult As Integer) As Integer Private Declare Function RegCloseKey Lib “advapi32.dll“ (ByVal hKey As Integer) 中 级 篇 167167 As Integer Private Declare Function RegE
3、numKey Lib “advapi32.dll“ Alias “RegEnumKeyA“(ByVal hKey As Integer, ByVal dwIndex As Integer, ByVal lpName As String, ByVal cbName As Integer) As IntegerConst HKEY_CURRENT_USER As Integer = uid=QSUser; pwd=QSPassword;database=northwind“)mySqlCommand = new SqlCommand(“select * from customers“, mySql
4、Connection)try输出字段名称 mySqlConnection.Open()myReader = mySqlCommand.ExecuteReader()Console.Write(“Customer ID “)Console.WriteLine(“Company Name“)输出纪录 do while (myReader.Read()Console.Write(myReader(“CustomerID“).ToString() + “ “)Console.WriteLine(myReader(“CompanyName“).ToString()loopcatch e as Excep
5、tionConsole.WriteLine(e.ToString()finallyif Not (myReader is Nothing)myReader.Close()end ifif (mySqlConnection.State = ConnectionState.Open)mySqlConnection.Close()end ifend tryend sub end class end namespace运行程序打开“开始|程序|Microsoft Visual Studio.NET7.0|Visual Studio.NET Tools|Visual Studio.NET Command
6、 Prompt” ，运行之后输入 vbc adooverview3.vb。即可生成可执行文件。小结ADO.NET 是 ADO 数据控制模型的升级版本，它是为了适应 Web 不断增长的规模而 设计的。ADO.NET 仍然使用以前的 ADO 对象，像 Connetion 和 Command 对象，同时还 增加了一些新的 ADO.NET 对象，如 DataSet、DataReader 和 DataAdapter 等。 ADO.NET 和以前 ADO 数据结构最大的不同就在于DataSet 对象，他跟以前任何 的数据存储都不同。正因为如此，DataSet 函数作为一个独立的实体而存在。在 DataSe
7、t 内 部，包括像表、关系、限制、视图等等跟一个数据库一样。实例 60：打印和打印预览功能实例说明在本实例中，我们将制作一个能实现打印和打印预览功能的应用程序。程序运行结果 如图 60-1 所示。图 60-1 运行结果技术要点打印预览功能的实现 打印功能的实现实现过程新建项目打开 Visual Studio.NET，选择“新建项目” ，在项目类型窗口中选择“Visual Basic 项 目” ，在模板窗口中选择“Windows 应用程序” ，在名称域中输入“PrintExample” ，然后选 择保存路径。单击“确认” 。添加控件和设置属性向当前窗体上添加三个 Button 控件，将他们的 T
8、ext 属性改为和界面一致。添加组件类和要打印的文件通过菜单“项目|添加组件”为当前项目添加一个组件类，并添加一个需要打印的文 件。186186 中 级 篇添加代码组件类中的代码 Imports System Imports System.ComponentModel Imports System.Windows.Forms Imports System.Drawing Imports System.Drawing.Printing Imports System.IO Namespace Microsoft.Samples.WinForms.VB.PrintingExample5Public
9、Class TextFilePrintDocumentInherits PrintDocumentPrivate printFont As FontPrivate streamToPrint As StreamReaderPublic Sub New(streamToPrint As StreamReader)MyBase.NewMe.streamToPrint = streamToPrintEnd SubOverride OnBeginPrint to set up the font we are going to useOverrides Protected Sub OnBeginPrin
10、t(ev As PrintEventArgs)MyBase.OnBeginPrint(ev)printFont = new Font(“Arial“, 10)End SubOverride the OnPrintPage to provide the printing logic for the documentOverrides Protected Sub OnPrintPage(ev As PrintPageEventArgs)MyBase.OnPrintPage(ev)Dim lpp As Single = 0Dim yPos As Single = 0Dim count As Inte
11、ger = 0Dim leftMargin As Single = ev.MarginBounds.LeftDim topMargin As Single = ev.MarginBounds.TopDim line as StringWork out the number of lines per pageUse the MarginBounds on the event to do thislpp = ev.MarginBounds.Height / printFont.GetHeight(ev.Graphics)Check count first so that we dont read
12、line that we wont printline=streamToPrint.ReadLine()While (count Nothing) Thenev.HasMorePages = TrueElseev.HasMorePages = FalseEnd IfEnd SubEnd Class End Namespace 主窗体中的代码 Imports System Imports System.ComponentModel Imports System.Windows.Forms Imports System.Drawing Imports System.Drawing.Printing
13、 Imports System.IO Namespace Microsoft.Samples.WinForms.VB.PrintingExample5Public Class PrintFormInherits System.Windows.Forms.FormPrivate storedPageSettings As PageSettingsPublic Sub New ()MyBase.NewPrintForm = MeInitializeComponent()AddHandler printButton.Click, AddressOf printButton_ClickAddHandl
14、er pageSetupButton.Click, AddressOf pageSetupButton_ClickAddHandler printPreviewButton.Click, AddressOf printPreviewButton_ClickEnd Sub页面设置Private Sub pageSetupButton_Click(sender As object, e As System.EventArgs)TryDim psDlg As New PageSetupDialogIf (storedPageSettings Is Nothing) ThenstoredPageSet
15、tings = new PageSettings()End IfpsDlg.PageSettings = storedPageSettingspsDlg.ShowDialogCatch ex As ExceptionMessageBox.Show(“An error occurred - “ + ex.Message)End TryEnd Sub开始打印Private Sub printButton_Click(sender As object, e As System.EventArgs)TryDim streamToPrint As StreamReader = new StreamRea
16、der (“PrintMe.Txt“)188188 中 级 篇Try使用缺省打印机Dim pd As TextFilePrintDocument = new TextFilePrintDocument(streamToPrint)If Not (storedPageSettings Is Nothing) Thenpd.DefaultPageSettings = storedPageSettingsEnd IfDim dlg As New PrintDialog()dlg.Document = pdDim result As DialogResult = dlg.ShowDialog()If (result = System.Windows.Forms.DialogResult.OK) Thenpd.Print()End IfFinallystreamToPrint.Close()End TryCatch ex As ExceptionMessag
