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VB.NET 與 XML 的實例操作
編輯:XML詳解     
再建立項目的文件夾的bin文件夾下
  
  '創建兩個文件
  
  '一個是"myxml.XML"
  
  '一個是"myXML.mdb"
  
  '這裡面有一個表"users"三個字段名"nameid","age","faverity"
  
  
  '再轉到圖形界面
  
  '單擊"工具箱"的"數據"把"OleDbConnection"," OleDbComman","DataSet","OleDbDataAdapter"
  
  '拉入窗體界面
  
  '依次對這幾個控件進行操作
  
  '我的文件夾是D:\vbproject\WindowsApplication1
  
  'D:\vbproject\WindowsApplication1/bin/myxml.XML
  
  'D:\vbproject\WindowsApplication1/bin/myXML.mdb
  
  //======================准備結束==============
  
  (1)首先在機子上要有.Net FrameWork
  
  打開VS.Net依次展開:文件-新建-項目;
  
  再選擇VISUAL-BASIC-項目-Windows應用程序

  這就是所需要一個小界面
  
  現在一步步的來寫代碼,完成它的功能
  
  首先來完成添加功能:
  
  我們目標是:通過這三個文本框(姓名,年齡,愛好)來添加到數據庫中。然後再把這個數據庫的表保存成XML格式
  
  雙擊"添加"按鈕
  
  在裡面寫下以下這些代:(VB寫的語言,不是C#)
  
  If TextBox1.Text <> "" And TextBox2.Text <> "" And TextBox3.Text <> "" Then
  
  '在三個文本框都不為空時,執行以下操作,
  
  '否則出錯
  Dim strsel As String
  strsel = "select * from users where nameid='" & TextBox1.Text & "'"
  
  '建立一個查詢字符串,看要要添加的姓名,是否已在數據中存在,如果不存在就可以添加
  OleDbCommand1 = New OleDbCommand
  Me.OleDbCommand1.CommandText = strsel
  Me.OleDbCommand1.Connection = OleDbConnection1
  OleDbConnection1.Open()
  Try
  
  '進行異常處理
  
  Dim reader As OleDbDataReader = OleDbCommand1.ExecuteReader()
  If reader.Read() Then
  
  '通過DataReader來讀取,如果讀得到,表明數據在有這個姓名存在,不添加;
  ListBox1.Items.Add("已經有該記錄!")
  Else
  reader.Close()
  
  '要對數據庫進行操作,首先把DataReader關掉;
  Dim insert As String
  insert = "insert into users(nameid,age,faverity) values('" & TextBox1.Text & "','" & TextBox2.Text & "','" & TextBox3.Text & "')"
  
  '建立一個插入字符串
  OleDbCommand1 = New OleDbCommand
  Me.OleDbCommand1.CommandText = insert
  Me.OleDbCommand1.Connection = Me.OleDbConnection1
  Me.OleDbCommand1.ExecuteNonQuery()
  ListBox1.Items.Add("添加成功!!")
  
  '以下是把數據庫的數據保存為XML格式
  DataSet1 = New DataSet
  OleDbDataAdapter1 = New OleDbDataAdapter("select * from users", OleDbConnection1)
  OleDbDataAdapter1.Fill(DataSet1, "users")
  DataSet1.WriteXml("myxml.XML")
  End If
  Catch ex As Exception
  ListBox1.Items.Add("Errors!")
  End Try
  
  OleDbConnection1.Close()
  Else
  MessageBox.Show("請輸入完整!!")
  End If
  
  //==================接下來是對數據庫進行查詢===================
  
  '雙擊"查找"按鈕
  
  '寫入以下代碼
  
  If TextBox4.Text <> "" Then
  
  '還是和上面一樣如果文本框為空,就不執行,如果不為空,就執行下面的操作
  ListBox1.Items.Clear()
  
  '首先把listBox清空
  Dim searchtext As String
  searchtext = TextBox4.Text
  OleDbConnection1.Open()
  Dim selstring As String
  selstring = "select * from users where nameid like '%" & searchtext & "%'"
  
  ' 建立查詢字符串,可以支持模糊查詢
  OleDbCommand1 = New OleDbCommand
  Me.OleDbCommand1.CommandText = selstring
  Me.OleDbCommand1.Connection = OleDbConnection1
  
  '以下幾句是顯示匹配的條數
  DataSet1 = New DataSet
  OleDbDataAdapter1 = New OleDbDataAdapter(selstring, OleDbConnection1)
  OleDbDataAdapter1.Fill(DataSet1, "users")
  ListBox1.Items.Add("共有" & DataSet1.Tables("users").Rows.Count & "條匹配的記錄")
  ListBox1.Items.Add("-------------------------------------------------------------")
  Try
  
  '進行異常處理
  Dim cmdreader As OleDbDataReader = OleDbCommand1.ExecuteReader()
  
  While cmdreader.Read
  
  '注意這裡要用while
  
  '不然就無法進行循環,就只能進行一次查詢
  ListBox1.Items.Add(cmdreader("nameid").ToString())
  ListBox1.Items.Add(cmdreader("age").ToString())
  ListBox1.Items.Add(cmdreader("faverity").ToString())
  ListBox1.Items.Add("----------------------------------")
  End While
  
  cmdreader.Close()
  
  OleDbConnection1.Close()
  Catch ex As Exception
  ListBox1.Items.Add("Errors")
  End Try
  Else
  End If
  
  //================再把來XML文檔,以XML形式顯示在ListBox裡面
  
  雙擊"XML文檔" 寫進下面這些代碼:
  
  ListBox1.Items.Clear()
  
  ' 清空listBox
  Dim xtr As XmlTextReader = New XmlTextReader("myxml.XML")
  
  '創建成一個XmlTextReader讀取"myxml.XML"文檔
  While xtr.Read
  Select Case (xtr.NodeType)
  
  ' 咱們用select case 形式來選擇XML節點類型
  Case XmlNodeType.XMLDeclaration
  
  '先從ListBox裡寫進xml聲明=====XMLdeclaration
  ListBox1.Items.Add("<?XML version='1.0' encoding='gb2312'?>")
  
  '再依次顯示節點的名稱,值
  
  '包括根節點
  Case XMLNodeType.Element
  ListBox1.Items.Add("<" & xtr.Name & ">")
  Case XMLNodeType.Text
  ListBox1.Items.Add(xtr.Value)
  Case XMLNodeType.EndElement
  ListBox1.Items.Add("</" & xtr.Name & ">")
  
  End Select
  End While
  xtr.Close()
  
  '關閉XMLTextReader
  
  //========再把數據庫中所有數據顯示在ListBox中========
  
  '雙擊"查看全部"按鈕
  
  '寫入下面的一些代碼:
  
  ListBox1.Items.Clear()
  
  '這些代碼大家應該可以看得懂了
  OleDbConnection1.Open()
  Dim selall As String
  selall = "select * from users"
  OleDbCommand1 = New OleDbCommand
  Me.OleDbCommand1.CommandText = selall
  Me.OleDbCommand1.Connection = OleDbConnection1
  Try
  Dim creader As OleDbDataReader = OleDbCommand1.ExecuteReader()
  While creader.Read
  ListBox1.Items.Add("name: " & creader("nameid").ToString() & "; age :" & creader("age").ToString() & "; faverity :" & creader("faverity").ToString())
  End While
  creader.Close()
  Catch ex As Exception
  ListBox1.Items.Add("Errors")
  End Try
  OleDbConnection1.Close()
  
  //==========================再來進完成刪除按鈕=================
  
  '雙擊"刪除"按鈕
  
  '寫入以下的代碼
  
  If TextBox4.Text <> "" Then
  
  '如果不為空,進行以下操作
  ListBox1.Items.Clear()
  
  '先清空ListBox
  OleDbConnection1.Open()
  
  ' 建立連接
  Dim delstring As String
  delstring = TextBox4.Text
  Dim delsel As String
  delsel = "select * from users where nameid='" & delstring & "'"
  
  '創建查詢字符串
  OleDbCommand1 = New OleDbCommand
  Me.OleDbCommand1.CommandText = delsel
  Me.OleDbCommand1.Connection = OleDbConnection1
  Try
  Dim selreader As OleDbDataReader = OleDbCommand1.ExecuteReader()
  If Not selreader.Read Then
  
  '假如讀不到,就表明數據庫無此數據,無法進行刪除操作
  MessageBox.Show("數據庫中無該記錄!")
  Else
  selreader.Close()
  
  '要對數據進行操作,必須首把DataReader關掉
  Dim delrecord As String
  delrecord = "delete * from users where nameid='" & delstring & "'"
  
  '建立刪除字符串sql語句,以上都是
  OleDbCommand1 = New OleDbCommand
  Me.OleDbCommand1.CommandText = delrecord
  Me.OleDbCommand1.Connection = OleDbConnection1
  Me.OleDbCommand1.ExecuteNonQuery()
  MessageBox.Show("刪除成功!!")
  
  '再把進行刪除操作的數據庫,再次把數據庫中數據保存成XML文檔
  DataSet1 = New DataSet
  OleDbDataAdapter1 = New OleDbDataAdapter("select * from users", OleDbConnection1)
  OleDbDataAdapter1.Fill(DataSet1, "users")
  DataSet1.WriteXml("myxml.XML")
  End If
  Catch ex As Exception
  MessageBox.Show(ex.Message)
  Finally
  OleDbConnection1.Close()
  End Try
  Else
  MessageBox.Show("請輸入你想刪除的記錄!")
  End If
  
  //======================= 重設按鈕=====
  
  TextBox1.Text = ""
  TextBox2.Text = ""
  TextBox3.Text = ""
  ListBox1.Items.Clear()
  
  //============================關閉===============
  
  me.Close()
  
  '好了這個小軟件完成了,有問題的話留言
  
  '本程序在.Net framework 2003創建
  
  '已經進行過測試,完全可以運行
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