you also can use this code
Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
If Len(TextBox1.Text) >= 3 Then
TextBox1.AutoCompleteMode = AutoCompleteMode.Suggest
TextBox1.AutoCompleteSource = AutoCompleteSource.AllUrl
Else
TextBox1.AutoCompleteMode = AutoCompleteMode.None
TextBox1.AutoCompleteSource = AutoCompleteSource.None
End If
End Sub
nice one :)