Wenn ich meine App starte, erhalte ich viele Informationen wie diese:

System.Windows.Data Information: 10 : Cannot retrieve value using the binding and 
no valid fallback value exists; using default instead. 
BindingExpression:Path=Period; DataItem=null; target element is 'TextBlock' (Name=''); 
target property is 'Text' (type 'String')

System.Windows.Data Information: 10 : Cannot retrieve value using the binding and 
no valid fallback value exists; using default instead. 
BindingExpression:Path=DocumentId; DataItem=null; target element is 'TextBlock' (Name=''); 
target property is 'Text' (type 'String')

Sollte ich für diese Ausgabe sorgen?