How to navigate a string message and a list and retrieve it into another page using WP8 c#

Question

In my windows phone application, I have two pages CreateGroups and GroupOfContacts and I want to navigate a list and string message from CreateGroups into GroupOfContacts page using button like below:

        private void btn_Click(object sender, RoutedEventArgs e)
        {
List<CustomContact> contact = new List<CustomContact>();
            PhoneApplicationService.Current.State["contactlist"] = contact;
            NavigationService.Navigate(new Uri("/GroupOfContacts.xaml?msg=" + buttonName, UriKind.RelativeOrAbsolute));
            NavigationService.Navigate(new Uri("/GroupOfContacts.xaml?contactlist=" + contact, UriKind.RelativeOrAbsolute));
        }

And I getting string message into GroupOfContacts page like below:

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
    base.OnNavigatedTo(e);

    string msg = "";
    if (NavigationContext.QueryString.TryGetValue("msg", out msg))
    {
        tblk_GroupName.Text = msg;
    }
    if (PhoneApplicationService.Current.State["contactlist"] != null)
    {
        listcontact = (List<CustomContact>)(PhoneApplicationService.Current.State["listOfContact"]);
    }  
}

But its getting me exception at this line listcontact = (List<CustomContact>)(PhoneApplicationService.Current.State["listOfContact"]);

Excetion is below:

A first chance exception of type 'System.Collections.Generic.KeyNotFoundException' occurred in mscorlib.ni.dll

Additional information: The given key was not present in the dictionary.

Is there any way to resolve it OR kindly suggest how to navigate a string message and a list together and retrieve from other page using WP8 c#. help me waiting for your reply. Thanks.

Answer 1

When you need to pass multiple parameters using NavigationService, what you should do is use the "&". But here you need to pass a list. So this wont suffice.

Try if this helps.

    private void hyplnk_Next_Click(object sender, RoutedEventArgs e)
    {
      NavigationService.Navigate("/GroupOfContacts.xaml?msg=" +buttonName+ "&listOfContact=1", listOfContact); 
    }

and access it on the other page like ::

protected override void OnNavigatedTo(NavigationEventArgs e) 
{ 
       // Store test data. 
       List<CustomContact> listContacts = new List<CustomContact>(); 

       string msg;
       if (NavigationContext.QueryString.TryGetValue("msg", out msg))
       {
           tblk_GroupName.Text = msg;
       }

       // Request parameter. The identification of the source page. 
       string parameter = NavigationContext.QueryString["listOfContact"]; 

       switch (parameter) 
       { 
           case "1": 
               var myParameter = NavigationService.GetLastNavigationData(); 


               if (myParameter != null) 
               { 
                   listContacts = (List<CustomContact>)myParameter; 
               } 
               break; 
       }
}

Hope it helps :)

Answer 2

You can also define variables in App class (app.xaml.cs) as public static variables and access them from any page by using

App.buttoName