Windows Phone MVVM + Prism — Convert Event to a command

Question

I am having trouble converting an eventhandler into a command using MVVM design and the Prism toolkit.

I'm also using the WPToolkit -- the DatePicker. I need to set the ValueChanged event to a command.

Here's my code:

MainPageViewModel

_setDateOne = new DelegateCommand(delegate()
     { });

void picker1_ValueChanged(object sender, DateTimeValueChangedEventArgs e)
{
   using (var isf = IsolatedStorageFile.GetUserStoreForApplication())
{
   if (isf.FileExists("DateOne"))
       isf.DeleteFile("DateOne");
 IsolatedStorageSettings.ApplicationSettings["DateOne"] = e.NewDateTime.Value;
 IsolatedStorageSettings.ApplicationSettings.Save();
}
}

Xaml

<toolkit:DatePicker Name="picker1" ValueChanged="picker1_ValueChanged" Value="{Binding DateOne, ElementName=this, Mode=TwoWay}"/>

I know the XAML is wrong; I don't know how to do it properly, yet.

Sorry, I'm pretty newbie with programming and especially MVVM.

Answer 1

No need of ValueChanged event handler here, you can do procedure to save selected date in setter of DateOne :

private DateTime _dateOne;
public DateTime DateOne
{
    get { return _dateOne; }
    set
    {
        _dateOne = value;
        SaveDate(value);
        NotifyPropertyChanged("DateOne");
    }
}

SaveDate(DateTime date)
{
    using (var isf = IsolatedStorageFile.GetUserStoreForApplication())
    {
        if (isf.FileExists("DateOne"))
           isf.DeleteFile("DateOne");
        IsolatedStorageSettings.ApplicationSettings["DateOne"] = date;
        IsolatedStorageSettings.ApplicationSettings.Save();
    }
}

And assuming DataContext of your page has been set properly, binding this way is enough :

<toolkit:DatePicker Name="picker1" Value="{Binding DateOne, Mode=TwoWay}"/>