此行/此列 不存在

Question

  Public Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles MyBase.Load 
        Try             Dim Conn As New OleDbConnection("Provider=SQLOLEDB;" & "Data Source=localhost;" & "Initial Catalog=test;User ID=sa;password=123")             Dim Sqlstr As String = "select Subject,article from board where ArticleNo=30 " 
            Dim Cmd As New OleDbCommand(Sqlstr, Conn) 
            Dim reader As OleDbDataReader 
            Conn.Open() 
            reader = Cmd.ExecuteReader() 
            Label1.Text = reader("Subject") **** 它说 不存在此行/此列.....我数据库明明有字段的~~~~ 
            Conn.Close() 
        Catch err As Exception 
            Label1.Text = "Error reading the database." 
            Label1.Text &= err.Message 
        End Try 
    End Sub

Answer 1

Label1.Text = reader.files("Subject") **** 它说 不存在此行/此列.....我数据库明明有字段的~~~~ 

Answer 2

'.Net的写法应该是这样的Imports System.Data.SqlClient
Public Class Form1    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click        Dim conn As New SqlConnection()
        Dim Cmd As New SqlCommand("select * from Employees ", conn)
        ' Cmd.CommandText = "select * from employee "
        conn.ConnectionString = "Data Source=.;Initial Catalog=Northwind;Persist Security Info=True;User ID=sa;Password="
        Dim reader As SqlDataReader
        Dim previousConnectionState As ConnectionState = conn.State
        Try
            If conn.State = ConnectionState.Closed Then
                conn.Open()
            End If
            reader = cmd.ExecuteReader()
            Using reader
                While reader.Read                    Console.WriteLine(reader.GetValue(0))   '指定的列
                    Console.WriteLine(reader.Item("LastName"))  '按列名取值
                End While
            End Using
        Finally
            If previousConnectionState = ConnectionState.Closed Then
                conn.Close()
            End If
        End Try    End Sub
End Class