ERROR[IM002][Microsoft][ODBC驱动程序管理器]未发现数据源名称并且未指定默认驱动程序,该怎么处理

ERROR[IM002][Microsoft][ODBC驱动程序管理器]未发现数据源名称并且未指定默认驱动程序
还是上次的实践作业：要求用VB2010+ACCESS2007做一个选择省出现对应城市的二级联动

现在代码已经写到这里：
Public Class Form1
  Public connectionstring As String  
  Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
  connectionstring = "Provider = Microsoft.ACE.OLEDB.12.0;Data Source=" & My.Application.Info.DirectoryPath & "\MyDB.accdb;"  
  Dim querystring As String = "select * from cs"  
  Dim conn As New OleDb.OleDbConnection(connectionstring)  
  Try
  conn.Open()  
  Dim cmd As New OleDb.OleDbCommand(querystring, conn)  
  Dim reader As OleDb.OleDbDataReader  
  reader = cmd.ExecuteReader()  
  ComboBox1.Items.Clear()  
  While (reader.Read())  
  If (ComboBox1.Items.Contains(reader.GetValue(1))) Then  
  Continue While  
  Else
  ComboBox1.Items.Add(reader.GetValue(1)) 
  End If
  End While
  reader.Close()
  Catch ex As Exception
  MsgBox(ex.Message)
  End Try
  End Sub
  Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
  Dim querystring As String = "select distinct city from cs where province = '" & ComboBox1.Text & " ' "
  Try
  Using connection As New Odbc.OdbcConnection(connectionstring)
  Dim command As New Odbc.OdbcCommand(querystring, connection)
  connection.Open()
  Dim reader As Odbc.OdbcDataReader = command.ExecuteReader
  ComboBox2.Items.Clear()
  While reader.Read
  ComboBox2.Items.Add(reader.GetValue(0))
  End While
  reader.Close()
  End Using
  Catch ex As Exception
  MsgBox(ex.Message)
  End Try
  End Sub
End Class

如果不加ComboBox1_SelectedIndexChanged这段程序可以正常执行，可加了之后，当选择省时出现错误提示：
ERROR[IM002][Microsoft][ODBC驱动程序管理器]未发现数据源名称并且未指定默认驱动程序


网上有提示要配置数据源的,照做了,但不好用,谁能告诉我为什么?我应该怎么弄?具体一点.如果把VS2010换成2008应该怎么办?


------解决方案--------------------
亲，这里是vb，要到。net区问。