object reference is required for the non-static field, method, or property

Question

hmm I seem to have a problem, on my main window I am trying to do this: ``` public static readonly DependencyProperty StudentIDProperty = DependencyProperty.Register("StudentID", typeof(String), typeof(LoginWindow), new PropertyMetadata(OnStudentIDChanged)); public string StudentID { get { return (string)GetValue(StudentIDProperty); } set { SetValue(StudentIDProperty, value); } } static void OnStudentIDChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { (d as LoginWindow).OnStudentIDChanged(e); // } ``` On my other window I have this: ``` MainWindow.StudentID = (String)((Button)sender).Tag; ``` But I get the error: ``` An object reference is required for the non-static field, method, or property 'WpfApplication4.MainWindow.StudentID.get' ``` Does anyone know how I can fix this? It works for my user controls but not other windows? My main window is actually named MainWindow so I may have had this confused.

Accepted Answer

You need to set StudentID on an instance of your MainWindow class. Try

```
((MainWindow)Application.Current.MainWindow).StudentID = (String)((Button)sender).Tag;
```

object reference is required for the non-static field, method, or property

Solution

Problem