Question

I implemented a sort of a wizard. With multiple windows. Each viewmodel of each window is a subclass of one base super class (also a viewmodel). In the first window, i fill up a property, which is in the base class. But in the next window, if i want to get that property, it is null. This is quite annoying and i really don’t know how this come.

This is my BaseViewModel:

public abstract class WijzigToetsBaseViewModel : INotifyPropertyChanged
    {
        #region Fields

       Examination exam;           

        #endregion // Fields

        #region Constructor

        protected WijzigToetsBaseViewModel()
        {

        }



        #endregion // Constructor

        #region Properties

        public Examination Examination
        {
            set { if(value != null)
                exam = value; this.OnPropertyChanged("Examination");
            }
            get { return exam; }
        }

So i the “shared” property is examination, in the first window , i fill this up by:

(viewmodel of the first window, implements model above)

 public string Pad
        {
            get { return pad; }
            set { pad = value;
            OnPropertyChanged("Pad");

            this.Examination = XmlConversionExamination.ReadExamination(value);
            Naam = this.Examination.Name;
            }
        }

But then, if i want to get the property “examination” in the second window,it gives null:

 public string Test
        {
            get {

                    return this.Examination.Name;             
            }
            set { test = value;
            OnPropertyChanged("Test");
            }
        }

(this is in second viewmodel, also implements base viewmodel.) so here this.Examination = null. This is kind of strange because i setted Examination property in the first window. Someone who has an idea?
Thanks

Answer 1

If you have two different ViewModels, then you thereby have two instances of the “base” ViewModel. So this is expected since Examination is an instance property.