We Keep Coding

Trying to Filter a bound ObservableCollection to a combobox based on another ComboBox Value not working

I see several other posts about this but I cannot seem to understand exactly how to get this working properly for my usage.
Here is what I have in a nutshell.
I have two Comboboxes--Role and Position.
I have both of these bound to an ObservableCollection which has Enum Values Converted to strings loaded into it on instantiation.
<ComboBox x:Name="empRoleCB" ItemsSource="{Binding Role}" SelectedItem="{Binding RoleStr}"/>
<ComboBox x:Name="empPositionCB" ItemsSource="{Binding Pos}" SelectedItem="{Binding PosStr}"/>
In my ViewModel:
public abstract class EmployeeMenuVMBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected bool SetProperty<T>(ref T field, T newValue, [CallerMemberName] string propertyName = null)
{
if(!EqualityComparer<T>.Default.Equals(field, newValue))
{
field = newValue;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
return true;
}
return false;
}
}
class EmployeeMenuVM : EmployeeMenuVMBase
{
private ObservableCollection<string> _pos = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Positions)));
private ObservableCollection<string> _role = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Roles)));
public ObservableCollection<string> Pos { get => _pos; }
public ObservableCollection<string> Role { get => _role; }
public string RoleStr
{
get => _roleStr;
set => SetProperty(ref _roleStr, value);
}
public string PosStr
{
get => _posStr;
set => SetProperty(ref _posStr, value);
}
}
What I want to happen is when a Role is selected, based on that selection, only certain Positions should be shown. For instance if I select "Customer Service" as a Role, then Position should only contain "Manager", "CSS" and "None". If Role is "Admin" then Position should only contain "None", and so on and so forth.
The struggle I have is how to filter this properly. I see something with using CollectionViewSource but I am unsure how to get this to work with my example.
I have 5 roles and each role will have a different list of positions that need to be shown.
What is the best way to make this work with MINIMAL extra code or XAML?
One of the things I really dislike about WPF is seemingly simple things need huge amounts of code to make them work properly many times.

First, if you think that WPF is complicated. So, you are using it wrongly.
I suggest you to use the Filter of CollectionViewSource as flow:
<ComboBox x:Name="empPositionCB" ItemsSource="{Binding MyPositionFilter}" SelectionChanged="RoleComboBox_SelectionChanged" ....../>
public ICollectionView MyPositionFilter { get; set; }
//ctor
public MyUserControlOrWindow()
{
//Before InitComponent()
this.MyPositionFilter = new CollectionViewSource { Source = MyPosObservableCollection }.View;
InitComponent();
}
public void RoleComboBox_SelectionChanged(object sender,EventArgs e)
{
//Get the selected Role (the ? is to prevent NullException (VS 2015 >))
Role r = empRoleCB.SelectedItem as Role;
//Apply the filter
this.MyPositionFilter.Filter = item =>
{
//Make you sure to convert correcteley your Enumeration, I used it here like a class
Position p = item as Position;
//Put your condition here. For example:
return r.ToLowers().Contains(p.ToLower());
//Or
return (r != null && r.Length >= p.Length);
};
}
The filter does not change your Collection, All hidden item stay in your ObservableCollection.

This can all be done in your ViewModel by changing the value of the Positions (Pos) observable collection when the role changes.
class EmployeeMenuVM : EmployeeMenuVMBase
{
public EmployeeMenuVM()
{
var emptyPositions = new List<Global.Positions>()
{ Global.Positions.None };
_rolePositions.Add(Global.Roles.None, emptyPositions);
var customerServicePositions = new List<Global.Positions>()
{ Global.Positions.None, Global.Positions.CSS, Global.Positions.Manager };
_rolePositions.Add(Global.Roles.CustomerService, customerServicePositions);
}
private Dictionary<Global.Roles, List<Global.Positions>> _rolePositions = new Dictionary<Global.Roles, List<Global.Positions>>();
private string _roleStr;
private string _posStr;
private ObservableCollection<string> _pos = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Positions)));
private ObservableCollection<string> _role = new ObservableCollection<string>(Enum.GetNames(typeof(Global.Roles)));
public ObservableCollection<string> Pos
{
get => _pos;
set
{
SetProperty(ref _pos, value);
}
}
public ObservableCollection<string> Role
{
get => _role;
}
public string RoleStr
{
get => _roleStr;
set
{
if (SetProperty(ref _roleStr, value))
{
Global.Roles role = (Global.Roles)Enum.Parse(typeof(Global.Roles), value);
var positions = _rolePositions[role].Select(p => p.ToString());
Pos = new ObservableCollection<string>(positions);
}
}
}
public string PosStr
{
get => _posStr;
set => SetProperty(ref _posStr, value);
}
}

Here is a working tester code just to see the main idea of how to do the filtering:
MainWindow.xaml
<Window x:Class="WpfApplication3.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApplication3"
x:Name="ThisView"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="600">
<StackPanel Orientation="Horizontal">
<ComboBox ItemsSource="{Binding Path=Roles, ElementName=ThisView}"
SelectedItem="{Binding Path=SelectedRole, ElementName=ThisView}"
Width="300" Height="60"/>
<ComboBox ItemsSource="{Binding Path=PositionCollectionView, ElementName=ThisView}" Width="300" Height="60"/>
</StackPanel>
</Window>
MainWindow.xaml.cs
public partial class MainWindow : Window, INotifyPropertyChanged
{
public ICollectionView PositionCollectionView { get; set; }
public ObservableCollection<string> Roles { get; set; } = new ObservableCollection<string>();
public ObservableCollection<string> Positions { get; set; } = new ObservableCollection<string>();
private string _selectedRole = String.Empty;
public string SelectedRole
{
get { return _selectedRole; }
set
{
_selectedRole = value;
OnPropertyChanged();
//This Refresh activates the Filter again, so that every time you select a role, this property will call it.
PositionCollectionView.Refresh();
}
}
public MainWindow()
{
PositionCollectionView = CollectionViewSource.GetDefaultView(Positions);
PositionCollectionView.Filter = PositionsFilter;
//use you enums here
Roles.Add("Role1");
Roles.Add("Role2");
Roles.Add("Role3");
Roles.Add("Role4");
Positions.Add("Position1");
Positions.Add("Position2");
Positions.Add("Position3");
Positions.Add("Position4");
InitializeComponent();
}
private bool PositionsFilter(object position)
{
bool result = true;
//place your code according to the Role selected to decide wheather "position" should be in the position list or not
return result;
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
Hope it helps..

Why is this ListView not changing with changes to the bound property?

Basic question from a novice. I've been stuck on this and have read through a lot of material and several similar questions on SO; hopefully not a completely duplicate question. I simplified the code as much as I know how to.
I'm trying to make the ListView show a filtered ObservableCollection) property (as the ItemsSource?), based on the selection in the ComboBox.
Specifically, which "meetings" have this "coordinator" related to it.
I'm not seeing any data errors in the output while it's running and debugging shows the properties updating correctly, but the ListView stays blank. I'm trying to avoid any code-behind on the View, there is none currently.
Thanks!
public class ViewModel : INotifyPropertyChanged
{
private ObservableCollection<Meeting> meetings;
public ObservableCollection<Meeting> Meetings
{
get
{
return meetings;
}
set
{
meetings = value;
OnPropertyChanged("ListProperty");
OnPropertyChanged("Meetings");
}
}
private string coordinatorSelected;
public string CoordinatorSelected
{
get
{
return coordinatorSelected;
}
set
{
coordinatorSelected = value;
Meetings = fakeDB.Where(v => v.CoordinatorName == CoordinatorSelected) as ObservableCollection<Meeting>;
}
}
private ObservableCollection<string> comboProperty = new ObservableCollection<string> { "Joe", "Helen", "Sven" };
public ObservableCollection<string> ComboProperty
{
get
{
return comboProperty;
}
}
private ObservableCollection<Meeting> fakeDB = new ObservableCollection<Meeting>() { new Meeting("Joe", "Atlas"), new Meeting("Sven", "Contoso"), new Meeting("Helen", "Acme") };
public ObservableCollection<Meeting> ListProperty
{
get
{
return Meetings;
}
}
public class Meeting
{
public string CoordinatorName { get; set; }
public string ClientName { get; set; }
public Meeting(string coordinatorName, string clientName)
{
CoordinatorName = coordinatorName;
ClientName = clientName;
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
XAML:
<Window.Resources>
<local:ViewModel x:Key="VM"></local:ViewModel>
</Window.Resources>
<DockPanel DataContext="{StaticResource ResourceKey=VM}">
<ComboBox Margin="10" ItemsSource="{Binding ComboProperty}" SelectedItem="{Binding CoordinatorSelected}" DockPanel.Dock="Top"/>
<ListView Margin="10" ItemsSource="{Binding ListProperty, UpdateSourceTrigger=PropertyChanged}" DisplayMemberPath="ClientName"/>
</DockPanel>
Update:
This seems to show that the lambda is returning a Meeting object but the assignment to Meetings is failing. Is this an error in casting maybe?
Thanks again.

You always have to change a property's backing field before you fire a PropertyChanged event. Otherwise a consumer of the event would still get the old value when it reads the property.
Change the Meetings property setter like this:
public ObservableCollection<Meeting> Meetings
{
get
{
return meetings;
}
set
{
meetings = value;
OnPropertyChanged("ListProperty");
OnPropertyChanged("Meetings");
}
}

I believe I've found two solutions to the same problem. The error pointed out #Clemens was also part of the solution. The Meetings property problem is solved if I change ListProperty and Meetings to IEnumerable. Alternatively this approach without changing the type, which I believe invokes the collection's constructor with the filtered sequence as an argument.
set
{
coordinatorSelected = value;
var filteredList = fakeDB.Where(v => v.CoordinatorName == coordinatorSelected);
Meetings = new ObservableCollection<Meeting>(filteredList);
OnPropertyChanged("ListProperty");
}

Unable to populate DataGrid

I am trying to build a datagrid where columns are generated dynamically (this works fine) but I am unable to create bindings for the columns which update automatically (something like INotifyPropertyChanged).
Creating columns dynamically and want to use dictionary elements for binding which can be modified/added dynamically. No errors seen in debug output of visual studio.
I think I am really missing something minor here.
clicking button does not populate the second column
ViewModel:
class DataGridAttachedPropertyViewModel {
public ObservableCollection<DataGridColumn> ColumnCollection { get; set; }
public ObservableCollection<AttachedPropertyEmployee> SomEmployees { get; set; }
public ICommand myCommand { get; set; }
public DataGridAttachedPropertyViewModel() {
this.ColumnCollection = new ObservableCollection<DataGridColumn>();
DataGridTextColumn tc = new DataGridTextColumn();
tc.Header = "Sample Column";
// tc.Binding = new Binding("name");
Binding forCurrent = new Binding("SimpleDict[f]");
forCurrent.Mode = BindingMode.TwoWay;
tc.Binding = forCurrent;
DataGridTextColumn tt = new DataGridTextColumn();
tt.Header = "Column x";
// tc.Binding = new Binding("name");
Binding forTheCurrent = new Binding("SimpleDict[x]");
forTheCurrent.Mode = BindingMode.TwoWay;
tt.Binding = forTheCurrent;
myCommand = new DelegateCommand(ButtonBase_OnClick);
this.ColumnCollection.Add(tc);
this.SomEmployees = new ObservableCollection<AttachedPropertyEmployee>();
this.SomEmployees.Add(new AttachedPropertyEmployee("Rajat","Norwalk"));
this.SomEmployees.Add(new AttachedPropertyEmployee("Matthew", "Norwalk"));
}
public void ButtonBase_OnClick() {
foreach (var VARIABLE in SomEmployees) {
VARIABLE.SimpleDict["x"] = "x";
}
}
}
AttachedPropertyEmployee.cs
public class AttachedPropertyEmployee : INotifyPropertyChanged {
private Dictionary<string, string> dict;
public Dictionary<string, string> SimpleDict {
get { return this.dict; }
set
{
if (this.dict != value) {
this.dict = value;
this.NotifyPropertyChanged("SimpleDict");
}
}
}
public AttachedPropertyEmployee(string Name, string Address) {
this.SimpleDict = new Dictionary<string, string>();
SimpleDict["f"] ="b";
this.name = Name;
this.address = Address;
}
public string name;
public string address { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(string propName) {
if (this.PropertyChanged != null)
this.PropertyChanged(this, new PropertyChangedEventArgs(propName));
}
}
XAML:
<Window x:Class="LearnInteractivity.LearnDataGridAttachedProperty"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:LearnInteractivity"
mc:Ignorable="d"
Title="LearnDataGridAttachedProperty" Height="300" Width="300">
<!--
Put a datargrid and an attached property and update columns dynamincally.
-->
<StackPanel>
<DataGrid
local:DataGridColumnsBehavior.BindableColumns="{Binding ColumnCollection}"
x:Name="dgg"
AutoGenerateColumns="False"
ItemsSource="{Binding SomEmployees}"></DataGrid>
<Button Content="Populate" Command="{Binding myCommand}"></Button>
</StackPanel>

I see two problems here.
The first is that Dictionary<TKey,TValue> doesn't implement INotifyCollectionChanged, so when you change values in it, no event is raised and the UI never knows about it. You could look for an ObservableDictionary<K,V> and use that (IIRC there are a few implementations around), or you can do it the quick and dirty way:
public void ButtonBase_OnClick() {
foreach (var VARIABLE in SomEmployees) {
VARIABLE.SimpleDict["x"] = "x";
VARIABLE.NotifyPropertyChanged("SimpleDict");
}
}
That will notify the grid that SimpleDict has changed.
The second problem is that in the DataGridAttachedPropertyViewModel constructor, you forgot to add tt to ColumnCollection.
this.ColumnCollection.Add(tc);
this.ColumnCollection.Add(tt);
More thoughts:
I would be more comfortable adding something like this to AttachedPropertyEmployee:
public void SetColumValue(string key, string value) {
SimpleDict[key] = value;
NotifyPropertyChanged("SimpleDict");
}
And use that in your loop instead:
public void ButtonBase_OnClick() {
foreach (var VARIABLE in SomEmployees) {
VARIABLE.SetColumnValue("x", "x");
}
}
Incidentally, I'd change SimpleDict to Dictionary<String, Object> so you can support more types than just string, and leave formatting to the UI. And I might consider exposing a ReadOnlyDictionary<K,V> in the SimpleDict property, with the writable dictionary a private field -- so callers would have no choice but to use SetColumnValue(k,v) to set the column values.

SelectedItem only updates first row in database in WPF

I am developing an application to allow a user to enter their employee details of their company into a database. So far I am experimenting with WPF and trying to implement MVVM within my application while using Entity Framework.
I'm creating a Master-Detail application, and have been researching into how to achieve this using MVVM, as I'm very much new to it all.
One of the ways in which I have tried is by creating a property within my View-Model called SelectedEmployee and then binding it to a List View in my xaml, like so;
public Employee _SelectedEmployee;
public Employee SelectedEmployee
{
get
{
return _SelectedEmployee;
}
set
{
if (_SelectedEmployee == value)
return;
_SelectedEmployee = value;
OnPropertyChanged("SelectedEmployee");
}
}
<ListView HorizontalAlignment="Left" Name="listview" VerticalAlignment="Bottom" ScrollViewer.HorizontalScrollBarVisibility="Visible"
IsSynchronizedWithCurrentItem="True"
ItemsSource="{Binding LoadEmployee}" SelectionMode="Single" SelectedItem="{Binding SelectedEmployee, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Height="150" Grid.Row="1">
I then have a method that allows the user to update a SelectedItem within the List View. But this is where the problem occurs. When I select an item from the List View, it only updates the first row from the database and not the row I wanted to select.
Here's the method;
public void UpdateEmployee(Employee emp)
{
using (DBEntities context = new DBEntities())
{
emp = context.Employees.Where(e => e.EmployeeID == SelectedEmployee.EmployeeID).FirstOrDefault();
emp.Title = Title;
emp.FirstName = FirstName;
emp.Surname = Surname;
emp.Position = Position;
emp.DateOfBirth = DateOfBirth;
emp.Address = Address;
emp.Country = Country;
emp.Postcode = Postcode;
emp.PhoneNumber = PhoneNumber;
emp.MobileNumber = MobileNumber;
emp.FaxNumber = FaxNumber;
emp.Email = Email;
emp.NINumber = NINumber;
emp.ChargableResource = ChargableResource;
emp.ChargeOutRate = ChargeOutRate;
emp.TimeSheetRequired = TimeSheetRequired;
emp.WorkShift = WorkShift;
emp.BenefitsProvided = BenefitsProvided;
context.Employees.ApplyCurrentValues(emp);
context.SaveChanges();
}
}
I have bound my properties within my view model to the text-boxes within my xaml and then implementing OnPropertyChanged.
I am also using Commands to limit the amount of code-behind as its important for testability and maintainability.
Here is the command method to update;
private ICommand showUpdateCommand;
public ICommand ShowUpdateCommand
{
get
{
if (showUpdateCommand == null)
{
showUpdateCommand = new RelayCommand(this.UpdateFormExecute, this.UpdateFormCanExecute);
}
return showUpdateCommand;
}
}
private bool UpdateFormCanExecute()
{
return !string.IsNullOrEmpty(FirstName) ...
}
private void UpdateFormExecute()
{
UpdateOrganisationTypeDetail();
}
As I am new to MVVM, I'm not quite sure what I am doing wrong so would appreciate some input please :).

Then perhaps the problem is with your updating. I don't really understand what your trying to do with listview, but since it's not working in a simple datagrid this might help. it's not so much an answer as something that I wrote to find your error that happens not to contain your error. please do comment if anything is awry.
public partial class MainWindow : Window
{
private static MainViewModel _mainViewModel = new MainViewModel();
public static ObservableCollection<Employee> staff = new ObservableCollection<Employee>();
public MainWindow()
{
InitializeComponent();
this.DataContext = _mainViewModel;
dataGrid1.DataContext = staff;
listview.DataContext = staff;
Employee Employee1 = new Employee();
Employee1.name = "Jeff";
staff.Add(Employee1);
Employee Employee2 = new Employee();
Employee2.name = "Jefferson";
staff.Add(Employee2);
Employee2.name = "Tim";
}
}
public class Employee
{
public string name { get; set; }
}
public class MainViewModel : INotifyPropertyChanged
{
private string _SelectedEmployee;
public string SelectedEmployee
{
get { return _SelectedEmployee; }
set
{
_SelectedEmployee = value;
NotifyPropertyChanged("SelectedEmployee");
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}

ListBox not populated in WP7 after values return from web request

I am trying to build a simple application for WP7 from scratch. The List Box in MainPage.xaml looks like this:
<Grid x:Name="ContentPanel" Grid.Row="1" >
<ListBox x:Name="MainListBox" ItemsSource="{Binding result}" SelectionChanged="MainListBox_SelectionChanged">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding name}" TextWrapping="Wrap" />
<TextBlock Text="{Binding description}" TextWrapping="Wrap" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
In order to populate result and its elements, name and description, I need to fetch the values from a web server that responds with json for the get request I send. Since I need to make different calls to the server that respond with different json objects, I am maintaining different .cs files for each, independant of mainpage.cs (where i only initialize, define MainPage_Loaded and MainListBox_SelectionChanged). All the data is fetched and processed in the individual .cs files.
Now the problem is that when I make the httpwebrequest and the reponse is retrieved, the UI is loaded well before that. As I understand from other posts the BeginGetResponse becomes a background process and the UI is loaded to keep it reponsive. So to summarize before the web request is returned with the data from the server, the UI is loaded as blank since the data is not populated. Now I cannot use the Dispatcher to populate since I am not in MainPage.cs and so can't access the List Box directly. I tried callback also but with no success. Please help
MainPage.cs:
public partial class MainPage : PhoneApplicationPage
{
// Constructor
public MainPage()
{
InitializeComponent();
this.Loaded +=new RoutedEventHandler(MainPage_Loaded);
}
private void MainListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (MainListBox.SelectedIndex == -1)
return;
NavigationService.Navigate(new Uri("/DetailsPage.xaml?selectedItem=" + MainListBox.SelectedIndex, UriKind.Relative));
MainListBox.SelectedIndex = -1;
}
// Load data for the ViewModel Items
private void MainPage_Loaded(object sender, RoutedEventArgs e)
{
if (!App.ViewModel.IsDataLoaded)
App.ViewModel.LoadData();
}
}
LoadData() essentially initializes the request parameters, prepares URI and send the HTTP request to another function in another class (executeRequest.cs file) that gets the reponse and processes the request into objects that I could map to:
public void decodeJson<E>(HttpWebRequest request)
{
request.Method = "GET";
var reqresult = (IAsyncResult)request.BeginGetResponse(ResponseCallback<E>, request);
}
public void ResponseCallback<E>(IAsyncResult reqresult)
{
var request = (HttpWebRequest)reqresult.AsyncState;
var response = (HttpWebResponse)request.EndGetResponse(reqresult);
if (response.StatusCode == HttpStatusCode.OK)
{
var stream = response.GetResponseStream();
var reader = new StreamReader(stream);
var contents = reader.ReadToEnd();
if (contents.ToString().StartsWith("{\"jsonrpc"))
{
using (var ms = new MemoryStream(Encoding.Unicode.GetBytes(contents)))
{
Type typeofe = typeof(E);
var deserializer = new DataContractJsonSerializer(typeof(E));
E element = (E)deserializer.ReadObject(ms);
populateResult<E>(element);
}
}
}
}
In populateResult I am trying to populate the UI. But by the time control enters BeginGetResponse my UI is populated and in populateResult since the List Box, MainListBox is not accessible I cannot use the dispatcher to refresh the UI with the new data
To give more info, result is an ObservableCollection of a class that contains different properties that come in from the json
The populateResult is very simple:
private void processResult<E>(E element)
{
//Checking for the type of result so that I can map
string typeis = typeof(E).ToString();
if (typeis.EndsWith("MyViewModel")
{
App.ViewModel.result = (element as MyViewModel).result;
???
}
}
Probably I should admit this (???) is where I am stuck. The result collection is updated but not in the UI. The UI is still blank and I cannot access the MainListBox from populateRsult to update. Hope it is clear. Else please tell me
With due courtesy let me also provide with MyViewModel and the SubViewModel
MyViewModel:
public class MyViewModel : INotifyPropertyChanged
{
public MyViewModel()
{
this.result = new ObservableCollection<SubViewModel>();
}
public ObservableCollection<SubViewModel> result { get; set; }
private string _sampleProperty = "Sample Runtime Property Value";
public string SampleProperty
{
get
{
return _sampleProperty;
}
set
{
_sampleProperty = value;
NotifyPropertyChanged("SampleProperty");
}
}
public bool IsDataLoaded
{
get;
private set;
}
public void LoadData()
{
//Initialize all the parameters
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(string.Format
(uri with parameters);
request.Method = "GET";
//call the decide json to get the reponse and parse it
executeRequest execReq = new executeRequest();
execReq.decodeJson<MyViewModel>(request);
this.IsDataLoaded = true;
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
if (null != PropertyChanged)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
SubviewModel:
public class SubViewModel : INotifyPropertyChanged
{
private string _name;
public string name
{
get
{
return _name;
}
set
{
_name = value;
NotifyPropertyChanged("name");
}
}
private string _description;
public string description
{
get
{
return _description;
}
set
{
_description = value;
NotifyPropertyChanged("description");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
if (null != PropertyChanged)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}

I don't see anything about how you're binding what to your listbox. you have a binding to result in your xaml, but aren't showing the declaration of what it actually is. If it is an observable collection, your populateResult method should be pretty trivial, just updating the observable collection's contents with new data.
If you are re-creating the observable collection in populate result, instead of just changing its content, that could be your problem.
update:
The biggest issue (from what i can tell from your updated code) is that your view model isn't firing a property change when you set result. so you need to do one of two things:
a) add property change support on result like the view model class has for SampleProperty, so that when it gets modified, bindings see the change:
private ObservableCollection<SubViewModel> _result = new ObservableCollection<SubViewModel>();
public ObservableCollection Result
{
get
{
return _result;
}
set
{
_result = value;
NotifyPropertyChanged("Result");
}
}
// -- elsewhere --
private void processResult<E>(E element)
{
// (why were you using the type **name** to check the
// type of the result instead of just using `as`?)
var model = element as MyViewModel;
if (model != null)
{
App.ViewModel.Result = model.result;
}
}
b) or you need to not set result, but modify its contents since it is an observable collection already:
private void processResult<E>(E element)
{
var model = element as MyViewModel;
if (model != null)
{
// result is an ObservableCollection, so just modify its contents.
// anything bound to it will see the changes via collection change notifications
App.ViewModel.result.ClearItems();
foreach (var x in model.result)
App.ViewModel.result.Add(x);
}
}