How to register a event handler to the event of another class in constructor of MainPage.xaml.cs

Question

Situation:

• i have a MainViewModel class that contains a collection named
  “Problems” of type ItemViewModel class

• i have a loadData function in MainviewModel class where
  ItemViewModel class is instantiated and instances are added to
  Problems collection .

• i also have a public event Event1 that fires at the end of LoadData function.

Doubt :

I want to register the Event1 in constructor of MainPage.xaml.cs , so that it points to a eventhandler defined in MainPage.xaml.cs. How do it do it ?

Following is the code snippet from MainViewModel class , certain declarations have been skipped for sake of clarity

    public event EventDelegate Event1;
    public void LoadData()
    {
    //place RT  data here

        this.Problems.Add(new ItemViewModel() { ID = 0, ProblemName = "Fever"});
        this.Problems.Add(new ItemViewModel(){ID=1,ProblemName="Diarrhea"});
        this.Problems.Add(new ItemViewModel() { ID=2,ProblemName = "sprain" });
        this.Problems.Add(new ItemViewModel() { ID = 3, ProblemName = "bruise" });

        OnEvent1();
    }

   protected virtual void OnEvent1()
   {
       EventDelegate handler = Event1;
       if (handler!=null)
       {
           handler();
       }
   }

Answer 1

You must have set the DataContext of MainPage to MainViewModel , so get the instance and hook your event in constructor after InitializeComponent()

public MainPage()
{
   InitializeComponent();
   ......
   ((MainViewModel)DataContext).Event1 += HandlerName;
   ......
}

---

UPDATE

For comments:

We are wiring the event handler and event1 , shouldn't we write ((MainViewModel)DataContext).Event1 += new HandlerName.

No, you don't need to. Anyhow, you code won't work, have to use delegate name ie

((MainViewModel)DataContext).Event1 += new EventDelegate(HandlerName);

One stated earlier and one stated above are equivalent.

Second will the statement DataContext = App.ViewModel.MainViewModel; placed after InitializeComponent(); set the datacontext to MainViewModel.

Yeah it will, you can place it before or after InitializeComponent() and it will work.