Visual Basic.NET快速开发MIS系统

2002-11-29· ·黎宇 ··yesky

　　【摘 要】 本文介绍微软最新技术Visual Basic.NET在数据库开发方面的应用。结合数据库系统开发的知识，介绍了物理表操作的方法，利用Visual Basic.NET的面向对象的特征，利用类的继承知识，简化了数据库系统开发过程。

　　引言

　　以前版本的Visual Basic虽然号称自己是一种OOP（面向对象）编程语言，但却不是一个地地道道的OOP编程语言，最多只是半个面向对象的编程语言。但Visual Basic.NET已经是一种完全的面向对象的编程语言。他支持面向对象的所有基本特征：继承、多态和重载。这使得以前在Visual Basic中很难或根本实现不了的问题，在Visual Basic.NET中可以顺利的用简单的方法实现。

　　自定义数据操作类

　　定义一个数据访问的基类，并编写有关数据库操作的必要方法。

　　定义一个数据访问类，类名为CData。定义连接Oracle数据库的方法ConnOracle，获取数据集的方法GetDataSet, 获取物理表的方法GetDataTable, 向物理表中插入一行数据的方法Insert, 向物理表中删除数据的方法Delete, 向物理表中更新数据的方法Update。其实现方法不是本文的重点，在此仅给出代码，不作详细分析。代码如下：

Public Class CDataBase
Dim OleCnnDB As New OleDbConnection()

'连接Oracle数据库，ServerName:服务器名，UserId:用户名，UserPwd:用户密码
Public Function ConnOracle(ByVal ServerName As String, ByVal UserId As String, ByVal UserPwd As String) As OleDbConnection

　Dim OleCnnDB As New OleDbConnection()
　With OleCnnDB
　　.ConnectionString = "Provider=MSDAORA.1;Password='" & UserPwd & "';User ID='" & UserId & "';Data Source='" & ServerName & "'"
　　Try
　　　.Open()
　　Catch er As Exception
　　　MsgBox(er.ToString)
　　End Try
　End With
　mOleCnnDB = OleCnnDB
　Return OleCnnDB
End Function

'获取数据集。TableName：表名，strWhere：条件
Public Overloads Function GetDataSet(ByVal TableName As String, ByVal strWhere As String) As DataSet

　Dim strSql As String
　Dim myDataSet As New DataSet()
　Dim myOleDataAdapter As New OleDbDataAdapter()

　myOleDataAdapter.TableMappings.Add(TableName, TableName)
　strSql = "SELECT * FROM " & TableName & " where " & strWhere

　myOleDataAdapter.SelectCommand = New OleDbCommand(strSql, mOleCnnDB)
　Try
　　myOleDataAdapter.Fill(myDataSet)
　Catch er As Exception
　　MsgBox(er.ToString)
　End Try
　Return myDataSet
End Function

'获取物理表。TableName：表名
Public Overloads Function GetDataTable(ByVal TableName As String) As DataTable
　Dim myDataSet As New DataSet()
　myDataSet = GetDataSet(TableName)
　Return myDataSet.Tables(0)
End Function

'获取物理表。TableName：表名，strWhere：条件
Public Overloads Function GetDataTable(ByVal TableName As String, ByVal strWhere As String) As DataTable

　Dim myDataSet As New DataSet()
　myDataSet = GetDataSet(TableName, strWhere)
　Return myDataSet.Tables(0)
End Function

　'向物理表中插入一行数据。TableName：表名，Value：行数据，BeginColumnIndex：开始列
Public Overloads Function Insert(ByVal TableName As String, ByVal Value As Object, Optional ByVal BeginColumnIndex As Int16 = 0) As Boolean

　Dim myDataAdapter As New OleDbDataAdapter()
　Dim strSql As String
　Dim myDataSet As New DataSet()
　Dim dRow As DataRow
　Dim i, len As Int16

　strSql = "SELECT * FROM " & TableName
　myDataAdapter.SelectCommand = New OleDbCommand(strSql, mOleCnnDB)
　Dim custCB As OleDbCommandBuilder = New OleDbCommandBuilder(myDataAdapter)
　myDataSet.Tables.Add(TableName)
　myDataAdapter.Fill(myDataSet, TableName)
　dRow = myDataSet.Tables(TableName).NewRow
　len = Value.Length
　For i = BeginColumnIndex To len - 1
　　If Not (IsDBNull(Value(i)) Or IsNothing(Value(i))) Then
　　　dRow.Item(i) = Value(i)
　　End If
　Next
　myDataSet.Tables(TableName).Rows.Add(dRow)
　Try
　　myDataAdapter.Update(myDataSet, TableName)
　Catch er As Exception
　　MsgBox(er.ToString)
　　Return False
　End Try
　myDataSet.Tables.Remove(TableName)
　Return True
End Function

'更新物理表的一个字段的值。strSql：查询语句，FieldName_Value：字段及与对应的值
Public Overloads Sub Update(ByVal strSql As String, ByVal FieldName_Value As String)

　Dim myDataAdapter As New OleDbDataAdapter()
　Dim myDataSet As New DataSet()
　Dim dRow As DataRow
　Dim TableName, FieldName As String