求一個用VB.net操作access數(shù)據(jù)庫的例程

Imports System

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Imports System.Drawing

Imports System.ComponentModel

Imports System.Windows.Forms

Imports System.Data.OleDb

Imports System.Data

Public Class Form1

Inherits Form

Private components As System.ComponentModel.Container = Nothing

Private WithEvents lastrec As Button

Private WithEvents nextrec As Button

Private WithEvents previousrec As Button

Private WithEvents firstrec As Button

Private t_books As TextBox

Private t_nl As TextBox

Private t_xb As TextBox

Private t_xm As TextBox

Private t_id As TextBox

Private l_books As Label

Private l_nl As Label

Private l_xb As Label

Private l_xm As Label

Private l_id As Label

Private label1 As Label

Private myDataSet As DataSet

Private WithEvents button1 As Button

Private WithEvents button2 As Button

Private WithEvents button3 As Button

Private WithEvents button4 As Button

Private myBind As BindingManagerBase

Public Sub New ( )

MyBase.New ( )

GetConnected ( )

InitializeComponent ( )

End Sub

'清除在程序中使用過的資源

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

Public Sub GetConnected ( )

'創(chuàng)建一個數(shù)據(jù)連接

Dim strCon As String = " Provider = Microsoft.Jet.OLEDB.4.0 ;

Data Source = db.mdb "

Dim myConn As OleDbConnection = New OleDbConnection ( )

myConn.ConnectionString = strCon

Dim strCom As String = " SELECT * FROM person "

'創(chuàng)建一個 DataSet

myDataSet = New DataSet ( )

myConn.Open ( )

'通過OleDbDataAdapter對象得到一個數(shù)據(jù)集

Dim myCommand As OleDbDataAdapter = New OleDbDataAdapter

( strCom , myConn )

'把Dataset綁定books數(shù)據(jù)表

myCommand.Fill ( myDataSet , "person" )

'關(guān)閉此數(shù)據(jù)連接

myConn.Close ( )

End Sub

'插入數(shù)據(jù)記錄操作代碼

Private Sub button2_Click (ByVal sender As Object , _

ByVal e As System.EventArgs) Handles button2.Click

'判斷所有字段是否添完，添完則執(zhí)行，反之彈出提示

If ( t_id.Text "" And t_xm.Text ""

And t_xb.Text "" And t_nl.Text ""

And t_books.Text "" ) Then

Dim myConn1 As String = " Provider = Microsoft.Jet.OLEDB.4.0 ;

Data Source = db.mdb"

Dim myConn As OleDbConnection = New OleDbConnection ( myConn1 )

myConn.Open ( )

Dim strInsert As String = " INSERT INTO person ( id , xm , xb , nl

, zip ) VALUES ( " _

t_id.Text + " , '" _

t_xm.Text + "' , '" _

t_xb.Text + "' , " _

t_nl.Text + " , " _

t_books.Text + ")"

Dim inst As OleDbCommand = New OleDbCommand ( strInsert , myConn )

inst.ExecuteNonQuery ( )

myConn.Close ( )

myDataSet.Tables ( "person" ).Rows ( myBind.Position ).BeginEdit ( )

myDataSet.Tables ( "person" ).Rows ( myBind.Position ).EndEdit ( )

myDataSet.Tables ( "person" ).AcceptChanges ( )

Else

MessageBox.Show ( "必須填滿所有字段值！" , "錯誤！" )

End If

End Sub

VB.net中類的實例化

1.不正確

Dim abc As myClass，定義一個可以引用myClass類型對象的變量abc。這個abc變量存在于棧上。

abc=New myClass。New myClass創(chuàng)建myClass實例對象，這個對象存在于托管堆上。然后（同時）讓abc引用（指向）這個對象。

abc變量在棧上，而對象在托管堆上。

abc儲存的是對象的地址，而不是對象本身。

看下面的代碼

Dim a As myClass,b As myClass,c As myClass

a=New myClass

b=a

c=a

整個過程中只創(chuàng)建了一個myClass對象，位于托管堆上。

三個myClass類型的變量a、b、c位于棧上，都指向了這一個myClass對象

2.類的成員分 實例成員 和 靜態(tài)成員

實例成員 必須在實例對象上調(diào)用

靜態(tài)成員 可以直接調(diào)用，不需要實例對象。

關(guān)于VB.NET進(jìn)度條的實例

該實例有很多實現(xiàn)方法,下面介紹一種不同的給你:

首先要在窗體中載入以下控件:progressbar(進(jìn)度條),label(用來實時顯示文本提示),兩個timer(分別控制進(jìn)度條進(jìn)度的增減),然后用以下代碼就能實現(xiàn):

Public Class Form1

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

Timer1.Enabled = True

Timer1.Interval = 500

Timer2.Interval = 500

ProgressBar1.Value = 0

ProgressBar1.Maximum = 100

ProgressBar1.Minimum = 0

End Sub

'上述過程是設(shè)置控件的初始值,也可以在屬性面板設(shè)置

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick

ProgressBar1.Value += 1

Label1.Text = "當(dāng)前完成" ProgressBar1.Value "%"

If (ProgressBar1.Value = 100) Then

Timer1.Enabled = False

Timer2.Enabled = True

End If

End Sub

'timer1用來控制進(jìn)度的增加

Private Sub Timer2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer2.Tick

ProgressBar1.Value -= 1

Label1.Text = "當(dāng)前完成" ProgressBar1.Value "%"

If (ProgressBar1.Value = 0) Then

Timer1.Enabled = True

Timer2.Enabled = False

End If

End Sub

'time2用來控制進(jìn)度的減少

End Class

本文名稱：vb.net例程,VBNET
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