DataGridView二次数据填充问题
在Button1_Click后,现象是同一个表[SensorData]在DataGridView1中追加；DataGridView1.DataSource = Nothing没有起作用；
问题:Button1_Click多次后，怎样才能只显示一个不重复的表，谢谢

代码如下:
Private Sub ReadDB()

Dim constr As String = "provider=microsoft.jet.oledb.4.0;data source= " & Application.StartupPath & "\EyeForSensor.mdb "
Dim sqlstr As String = "Select * from SensorData order by Num asc "
Dim myconn As New OleDbConnection(constr)
Dim mycomm As New OleDbCommand(sqlstr, myconn)
myconn.Open()
adapter = New OleDbDataAdapter(sqlstr, myconn)

adapter.Fill(ds, "SensorData ")
DataGridView1.DataSource = ds.Tables( "SensorData ")
OLEB = New OleDbCommandBuilder(adapter)
'获取或设置指定其名称包含空格或保留标记等字符的数据库对象（例如，表或列）时使用的开始字符
OLEB.QuotePrefix = "[ "
OLEB.QuoteSuffix = "] "
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
DataGridView1.DataSource = Nothing
MsgBox( "重新装载test ") 'DataGridView1这里显示为空
ReadDB() '但是这里会把以前的填充都显示出来
End Sub

[解决办法]
在 adapter.Fill(ds, "SensorData ")　之前