VB.NET通过OleDbConnection连接oracle查询数据示例

本文实现了VB.Net通过OleDbConnection连接oracle查询数据，并展示数据到TextBox1。

select * from v$version; 

3.IDE版本

Microsoft Visual C++ 2019

Imports System.Data.OleDb

Public Class oracleDemo

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        '创建数据库连接
        Dim oleDbCon As New OleDbConnection
        '连接字符串192.168.31.55
        Dim conStr = "(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))
(CONNECT_DATA=(SERVICE_NAME=orcl)))"
        oleDbCon.ConnectionString = "Provider=OraOLEDB.Oracle;Data Source=" + conStr +
         ";user id=scott;password=root"
        'Command 对象提供执行 SQL命令的功能
        Dim oleDbCmd As New OleDbCommand()
        '打开连接
        oleDbCon.Open()
        '设置 Command 对象的连接属性
        oleDbCmd.Connection = oleDbCon
        '定义sql
        Dim sql = "select 'aa' from dual"
        '查询真正的数据库
        sql = "SELECt * FROM EMP --where empno = '7369'"
        oleDbCmd.CommandType = CommandType.Text
        '设置查询语句
        oleDbCmd.CommandText = sql
        'DataReader 对象提供只读方式的数据对象
        Dim dataRd As OleDbDataReader
        '查询数据
        dataRd = oleDbCmd.ExecuteReader()
        Dim a = "返回结果："

        '这样只能查询出第一条结果 
        'If dataRd.Read() Then
        '    a += CStr(dataRd.GetValue(0))
        'Else
        '    MsgBox("错误")
        'End If

        '这样能查询出全部数据
        While dataRd.Read = True
            a += CStr(dataRd.GetValue(0))
            'TextBox1.Text.Append(str)
            a += ","
        End While

        '在TextBox1中显示显示查询结果
        TextBox1.Text = a
        dataRd.Close()
        oleDbCon.Close()
    End Sub

End Class

提示这个异常做如下处理

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