The sad solution is: dont use the asp:ObjectDataSource...
Now Im using the asp:LinqDataSource wich provides a 'selecting'-event from where I can modify the Controls on my frontend.
' Selecting-Event from my LinqDataSource
private Sub myLinqDataSource_Selecting(sender .., e .. ) Handles myLinq..Selecting
dim mydata = DbManager.HeavyCall(..)
literalValueA.Text = (From i in mydata ..... ).Count ' works
literalValueB.Text = (From i in mydata ..Where ... ).Count ' works
e.Result = mydata
End Sub