hi there, im using the following code to load data into a datagrid and update it, but the update part isnt working fine, any ideas?

Dim conn As New OleDbConnection(connection_str)
conn.Open()
sql_str = "select * from num"

Dim objCommand As New OleDbCommand(sql_str, conn)

Dim DS As New DataSet()

data_adapter = New OleDbDataAdapter(objCommand)
data_adapter.Fill(ds, "to")

DataGrid1.DataSource = ds.Tables("to")

End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
'Dim ds As New DataSet()

If ds.HasChanges() Then
MsgBox("yes")
End If



the error msg is :
An unhandled exception of type 'System.NullReferenceException' occurred in datagridexple.exe

Additional information: Object reference not set to an instance of an object.


thank you.