I'm wondering what is the best way to pass a file between pages in a UWP app?
I have a UWP app with two pages. In the first page, I have the user open a file with filepicker and load that file into a media player.
I want to pass that same file onto the second page when the user navigates there. I am passing the file over currently as a string which I then am attempting load as a storagefile using GetFileFromPathAsync.
This currently works as I'm able to load the file on the second page but it requires that the user provide broad file system access.
Code on Page 1 (FileLoaded is file path string):
private async void TranscodeMedia_Click(object sender, RoutedEventArgs e)
{
AppWindow appWindow = await AppWindow.TryCreateAsync();
Frame appWindowContentFrame = new Frame();
appWindowContentFrame.Navigate(typeof(TranscodeMedia), FileLoaded);
Code on Page 2:
protected override async void OnNavigatedTo(NavigationEventArgs e)
{
var fileTransfer = e.Parameter.ToString();
FileName.Text = fileTransfer;
StorageFile PassedFile = await StorageFile.GetFileFromPathAsync(fileTransfer);
I'm wondering if this is the best way to pass the file between pages? I'd rather not require the user to provide broad system access to the app if possible. Any help you can provide is most appreciated!
The best and most standard way in C#/WPF/UWP way is to use a standard pattern that consist of a general ViewModel class (which contains all the common app data that you want to use in the logic layer), put as a field in the static MainPage (or even in the App.xaml.cs class).
I always do it like this:
1) I use the MainPage automatically created as the "shell" of the app, with a property that is the AppViewModel.
The MainPage (and thus the AppViewModel) can be accessed from everywhere in the app, by setting itself as a static field in its own class (the "Current" static field can be called from everywhere in the app... even in a MessageDialog class!).
This is the code for the MainPage (or a shell Page that you wish, but I suggest doing like this, it is a pretty standard way used even by Microsoft), simpler than you think:
public sealed partial class MainPage : Page
{
public AppViewModel ViewModel { get; set; } = new AppViewModel();
public static MainPage Current { get; set; }
public MainPage()
{
this.InitializeComponent();
Current = this;
}
}
THIS is the trick: to make the page static in one field in its
own class, so that that static field will be UNIQUE in the entire app
(this is one of the main features of the "static" word) and, thus, by calling
MainPage.Current.ViewModel you can immediately get any data (in your
specific case, a StorageFile) stored there.
2) The AppViewModel itself is a class that must implement the INotifyPropertyChanged interface, in order to enable bindable properties and functions.
It is common, among Windows developers, to create a base class that implements it and then derive all the classes that needs bindable (i.e. observable) properties from it.
Here it is, exactly how Microsoft itself creates it:
public class BaseBind : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged([CallerMemberName] string propertyName = null) =>
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
protected bool SetProperty<T>(ref T storage, T value,
[CallerMemberName] String propertyName = null)
{
if (object.Equals(storage, value)) return false;
storage = value;
OnPropertyChanged(propertyName);
return true;
}
}
Then you derive AppViewModel class (and all the other model and viewmodel classes) from it… populating it with all the common properties that you need to share across pages.
I have even added a derived property, in order to show how you can share even multiple data types at once, and a function:
public class AppViewModel : BaseBind
{
public AppViewModel()
{
// Usually we initialize all the starting data here, in the viewmodel constructor...
}
// All common app data
private string sampleCommonString;
public String SampleCommonString
{
get { return sampleCommonString; }
set { SetProperty(ref sampleCommonString, value); OnPropertyChanged(nameof(SampleDerivedProperty1)); OnPropertyChanged(nameof(SampleDerivedProperty2)); }
}
public String SampleDerivedProperty1 => "return something based on SampleCommonString";
public String SampleDerivedProperty2
{
get
{
// evaluate in some way SampleCommonString...
return "Same thing as SampleDerivedProperty1, but it allows to add more than just one istruction";
}
}
// This is a property that you can use for functions and internal logic… but it CAN'T be binded to the UI directly
public String SampleNOTBindableProperty { get; set; }
public void SampleFunction()
{
// Insert code, that needs to interact with all the data contained in the viewmodel itself, here...
// The function has to be with NO parameters, in order to work with simple {x:Bind} markup.
// If your function has to access some specific data, you can create a new bindable (or non) property, just as the ones above, and memorize the data there.
}
}
3) Then, in order to access all this from another Page, just create an AppViewModel field in that page, referencing the viewmodel contained in the static mainpage:
public sealed partial class SecondPage : Page
{
public AppViewModel ViewModel => MainPage.Current.ViewModel;
public SecondPage()
{
this.InitializeComponent();
}
}
...and you can easily bind XAML controls properties to the AppViewModel itself:
<TextBlock Text="{x:Bind ViewModel.SampleCommonString, Mode=OneWay}"/>
<TextBox Text="{x:Bind ViewModel.SampleCommonString, Mode=TwoWay}"/>
<Button Content="Sample content" Click="{x:Bind ViewModel.SampleFunction}"/>
(Mode=OneWay is for real-time binding, in order that the property is immediately updated even in the UI, while Mode=TwoWay is used for those properties that can be edited from the control itself, by the user, in order to interact with app logic).
In this mode you will be able to display data and all its changes in real-time!
So... this is the way to keep all the app data at run-time in a
correct and flexible way... by learning it and practicing, in the
future you will use this pattern even in a smarter way, by creating
viewmodels for every object of your application (for example: if
your app need to store your company's customers data, you will have a
"CustomerViewModel" class derived from the BaseBind class, with all
the data of a customer in it) and creating lists like
ObservableCollection<SampleViewModel> to store all of them (ObservableCollection<t> is a collection type that has built-in mechanism to handle list changes, like adding, removing and reordering list items).
Then you will link every observable collection to the ItemsSource property of a control that inherits from ListBase class (tipically: ListView or GridView), creating a DataTemplate to display each list item, like in this example:
<Page
xmlns:vm="using:SampleApp.ViewModelsPath"
<Grid>
<ListView ItemsSource="{x:Bind ViewModel.SampleListOfObjectViewModel, Mode=OneWay}">
<ListView.ItemTemplate>
<DataTemplate x:DataType="vm:SampleObjectViewModel">
<StackPanel>
<TextBlock Text="{x:Bind SampleObjectProperty1, Mode=OneWay}"/>
<TextBlock Text="{x:Bind SampleObjectProperty2, Mode=OneWay}"/>
<Button Click="{x:Bind SampleObjectFunction}"/>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</Grid>
</Page>
...and all the data displayed will be updated in real-time whenever you change it!
Hope this all will help you boost your knowledge about how preparing a WPF/UWP logic layer, because all of this works pretty in the same way even for the WPF apps (i.e. the old desktop programs).
Best regards
There are some other ways to implement your requirement about accessing the same file on different pages. But for your scenario, you could use Future-access list in your UWP app.
By picking files and folders, your user grants your app permission to access items that might not be accessible otherwise. If you add these items to your future-access list then you'll retain that permission when your app wants to access those items again later.
Here is the sample code I made
In the first page:
FileOpenPicker picker = new FileOpenPicker();
picker.FileTypeFilter.Add("*");
StorageFile file = await picker.PickSingleFileAsync();
if (file != null)
{
// add file to the Future Access list
var storageItemAccessList = Windows.Storage.AccessCache.StorageApplicationPermissions.FutureAccessList;
// this token is the key to get the file.
string FALToken = storageItemAccessList.Add(file, "mediaFile");
// in your real scenario, you need to save the token and pass it when you nee
this.Frame.Navigate(typeof(TestPage), FALToken);
}
In the second page:
protected override async void OnNavigatedTo(NavigationEventArgs e)
{
string token = (string)e.Parameter;
var storageItemAccessList = StorageApplicationPermissions.FutureAccessList;
StorageFile retrievedFile = await storageItemAccessList.GetFileAsync(token);
}
So you don't need the broad file system access if you use Future-access list to keep the permission of files.
For more detailed information, please refer to this document: Track recently used files and folders
Related
Please can you advise if this is possible or what approach is best?
I will add my code afterwards but I am worried that it will add limited value to what I am trying to ask/explain.
The WPF examples that I have seen implement
A (poco) model e.g Customer.
Then they implement a view model (MVVM pattern). (The View Model needs to implement ObservableCollection and or implement INotifyPropertyChanged interface so that any changes in the model are reflected in the UI once the model changes.)
In the xaml code behind, in the page constructor, the ViewModel is passed to the DataContext.
The xaml can then bind to this View Model Data with a Mode of update e.g. TwoWay.
Here is what I need to understand.
I have implemented my own data model / class, which has async tasks constantly updating the status of different fields in this class.
My model resides in a separate class library that I would like to inject/supply it to a view model. However, since my object/class is 'self-updating', I can't simply copy across values into my view model - since they will change over time. I want my view model to be aware of changes that underlying values and show these changes in the UI as the async tasks update the model.
How do I go about this? So in my example, my Customer object will be self-updating, some background task would add/remove customers in a class library outside of my ViewModel.
I hope that I have managed to ask my question in a way that is clear to understand.
The XAML binding to the Customer View Model
<ListView Grid.Row="1" ItemsSource="{x:Bind ViewModel.Customers,Mode=OneWay}"
SelectedItem="{x:Bind ViewModel.SelectedCustomer,Mode=TwoWay}">
<ListView.ItemTemplate>
<DataTemplate x:DataType="model:Customer">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{x:Bind FirstName,Mode=OneWay}" FontWeight="Bold"/>
<TextBlock Text="{x:Bind LastName,Mode=OneWay}"
Margin="5 0 0 0"/>
<TextBlock Text="(Developer)" Margin="5 0 0 0" Opacity="0.5"
Visibility="{x:Bind IsDeveloper,Mode=OneWay}"/>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
Reference for this sample code
public class MainViewModel : Observable
{
private ICustomerDataProvider _customerDataProvider;
private Customer _selectedCustomer;
public MainViewModel(ICustomerDataProvider customerDataProvider)
{
_customerDataProvider = customerDataProvider;
Customers = new ObservableCollection<Customer>();
}
public Customer SelectedCustomer
{
get { return _selectedCustomer; }
set
{
if (_selectedCustomer != value)
{
_selectedCustomer = value;
OnPropertyChanged();
OnPropertyChanged(nameof(IsCustomerSelected));
}
}
}
public bool IsCustomerSelected => SelectedCustomer != null;
public ObservableCollection<Customer> Customers { get; }
public async Task LoadAsync()
{
Customers.Clear();
var customers = await _customerDataProvider.LoadCustomersAsync();
foreach (var customer in customers)
{
Customers.Add(customer);
}
}
public async Task SaveAsync()
{
await _customerDataProvider.SaveCustomersAsync(Customers);
}
public void AddCustomer()
{
var customer = new Customer { FirstName = "New" };
Customers.Add(customer);
SelectedCustomer = customer;
}
public void DeleteCustomer()
{
var customer = SelectedCustomer;
if (customer != null)
{
Customers.Remove(customer);
SelectedCustomer = null;
}
}
}
The INotifyPropertyChanged is implemented here:
public class Observable : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName]string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
Thanks #Bandook for your comments. Sometimes the coding is the easy part, but the thought behind and the process of fitting the parts together in a simple and coherent way can be more difficult.
The solution I implemented was as follows:
As per the customer example, I had had to implement methods that updated my class properties that implemented the INotifyPropertyChanged interface. (This was almost identical to the Customer code.) The result of this is that any changes to the underlying model are reflected in the UI.
The kicker was this. I implemented a Publish Subscribe Design Pattern in my class library - that continually refreshed the data. My 'Customer' class had to then had to subscribe to change events published by the class library.
There was one problem, however, the thread for the Class Library code and that of the application thread was not the same, resulting in a clash.
The article here allowed me to solve this issue.
In summary, the solution was to implement a Publish Subscribe Design Pattern. My class library published updates and my View Model class (similar to the customer class) subscribed to the events it published.
I am using a navigation model that has a MainPage, which contains a hamburger menu and a MyFrame in a splitview. I have two pages, WorkingPage and SavePage, which are displayed in the MyFrame. So MainPage includes this:
<Page>
<!-- Other stuff -->
<SplitView>
<SplitView.Pane>
<!-- Other stuff -->
<ListBox Name="HamburgerMenuMenuItems"
SelectionChanged="HamburgerMenuMenuItems_SelectionChanged">
<ListBoxItem Name="HamburgerMenuItemSave">
<!-- Content -- >
</ListBoxItem>
</ListBox>
<!-- Other stuff -->
</SplitView.Pane>
<SplitView.Content>
<Frame Name="MyFrame"></Frame>
</SplitView.Content>
</SplitView>
<!-- Other stuff -->
</Page>
The user clicks Save, which is one of the items in the Hamburger menu (set up as a listbox), and which raises the selection changed event, on the MainPage, which results in MainPage initiating a navigation from WorkingPage to SavePage in MyFrame.
public sealed partial class MainPage : Page
{
private void HamburgerMenuMenuItems_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
// Other options similar ...
else if (HamburgerMenuItemSave.IsSelected)
{
MyFrame.Navigate(typeof(Pages.File.SavePage));
}
// Other options similar ...
}
}
WorkingPage contains a data member that I want SavePage to have access to.
This is what I have:
public sealed partial class WorkingPage : Page
{
public MyClass myClass;
// Other stuff ...
}
I want the value of "myClass" to be passed to SavePage, so it ultimately ends up as:
public sealed partial class SavePage : Page
{
public MyClass myClass;
// Other stuff ...
}
I know from research (and extensively using it myself) that the proper way to pass parameters between two pages is as follows:
Frame.Navigate(typeof(PageClass), someParameter);
But the problem is MainPage is where the navigation is initiated, but the needed parameter value to pass (myClass) only exists in the scope of WorkingPage. This thus requires that either:
A) the navigation be initiated by WorkingPage, so that I can use the line of code above, and just put in "SavePage" as the PageClass and "myClass" as the parameter, or
B) MainPage somehow needs to obtain knowledge of the value of "myClass", so that I can use the same line of code as (A), but with "this.MyFrame" instead of "Frame"
How can getting the value of "myClass" from WorkingPage to SavePage be accomplished, with a navigate event initiated from MainPage? This seems like a common need, but everything I have found only talks about the simple case of one page initiating navigation to another, when a parameter must be passed from the initiating page to the other.
I am pretty sure this can be done in different ways.. but personally I like to use following pattern to achieve this :
Firstly, in your MainPage you have to create sort of an utility method for the navigation :
public void navigateWithParameter(Page yourPage,String yourParameter){
MyFrame.Navigate(typeof(yourPage), yourParameter);
}
Next you can call this method from any page you want to (which in your case is the WorkingPage), by getting the current instance of the MainPage and calling the navigateWithParameter function with the appropriate parameters :
var frame = (Frame)Window.Current.Content;
var mainpage = (MainPage)frame.Content;
mainpage.navigateWithParameter(yourPage,"It works!");
Hope this helps!
Through further research, I found a way to address this issue (other ways may exist). There exists a property of a Frame that allows you to get a reference to the page the frame is currently displaying:
MyFrame.Content
Thus, on MainPage, in the event handler, you can obtain a reference to the page being displayed, which then allows you to access MyClass, since it is a public data member. You can then pass the value of MyClass into the page being navigated to... all without WorkingPage having any knowledge of the event firing.
public sealed partial class MainPage : Page
{
private void HamburgerMenuMenuItems_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
// Other options similar ...
else if (HamburgerMenuItemSave.IsSelected)
{
// 1. Check if the current page is the correct type
if (MyFrame.Content is WorkingPage workingPage)
{
// 2. Grab the data to pass from the instance of the displayed page
MyClass dataToPass = workingPage.myClass;
// 3. Pass the grabbed data to the page being navigated to
MyFrame.Navigate(typeof(Pages.File.SavePage), dataToPass);
}
}
// Other options similar ...
}
}
I had a similar task. I have a UWP page with a lot of settings, grouped buttons with binded NumberBoxes. To move out of MainPage all button handlers needed a "helper Class". There I passed the main page object, which automaticaly gives me access to all elements in my MainPage.
My XAML looked like is:
<Page> <Grid>
<StackPanel >
<muxc:NumberBox x:Name="Offset" PlaceholderText="0,35" />
<Button Content="GrOffset" Click="buttonClickHandler.Offset_Click" />
</StackPanel>
<TextBox x:Name="Messager_Container" Text="Total" />
<Grid/>
<Page/>
C# is
namespace Eval
{
public sealed partial class MainPage : Page
{ /// <summary>
/// An empty page that can be used on its own or navigated to within a Frame.
/// </summary>
ButtonClickHandler buttonClickHandler = new ButtonClickHandler(); // create a new instance of our "helper class"
//===================================
public MainPage()
{
this.InitializeComponent();
var mainPageVAR = this; // only for check ot, is it valid assigning
buttonClickHandler.mainPage = this; //assign to, we pass the addres to our MainPage class instance
}
public class ButtonClickHandler // our helping class
{
public Eval.MainPage mainPage;
public void Offset_Click(object sender, RoutedEventArgs e)
{
mainPage.Messager_Container.Text=
mainPage.Offset.Value.ToString();
// our value from numberBox "Offset" passed to TextBox "Messager_Container"
}
}
}
I am loving Template10 so far, very nice.
I am a little stuck though on how to bind to a Setting value on the Main Page.
I have added a new bool setting which is storing properly.
On my main page I have a Visibility binding to the setting:
Visibility="{Binding UseAmbientLightSensor, Converter={StaticResource CollapsedWhenFalseConverter}}"
This works on app start as expected, the MainPageViewModel reads the value from Settings and a grid is visible or collapsed based on that setting.
However I cannot seem to get this binding to 'listen' to the setting, if I go to the settings page and change that value, when I go back to the Main Page the visibility does not change. It only works if I restart the app.
In the vanilla Template10 install this would be akin to Binding a little logo on MainPage to the 'UseLightThemeButton' setting in the Settings page which changes based on that setting..
Okay, so I guess this is the "official" answer. But many approaches are valid. This one matches most closely to the templates. I would do it like this:
public class MainPageViewModel : ViewModelBase
{
Services.SettingService.SettingService _SettingService;
public MainPageViewModel()
{
_SettingService = Services.SettingService.SettingService.Instance;
}
public override async Task OnNavigatedToAsync(object parameter, NavigationMode mode, IDictionary<string, object> state)
{
Windows.Storage.ApplicationData.Current.DataChanged += SettingsChanged;
await Task.CompletedTask;
}
public override async Task OnNavigatedFromAsync(IDictionary<string, object> pageState, bool suspending)
{
Windows.Storage.ApplicationData.Current.DataChanged -= SettingsChanged;
await Task.CompletedTask;
}
private void SettingsChanged(Windows.Storage.ApplicationData sender, object args)
{
RaisePropertyChanged(nameof(FontSize));
}
public double FontSize { get { return _SettingService.FontSize; } }
}
With that view-model, you can easily bind to a setting (in this case FontSize).
Best of luck.
There are two possible scenarios that may not be happening:
Raise the property change event when your bool value gets updated.
Set the binding to a two way mode.
In order to do this change the binding mode of your Visibility property
Visibility="{Binding UseAmbientLightSensor, Mode=TwoWay, Converter={StaticResource CollapsedWhenFalseConverter}}"
This will tell xaml to listen to any change on the property in the view model.
Then you need to tell the View model when to let the XAML view know of its changes, if you are using Template10, then it can be done as follows:
private bool useAmbientLightSensor;
public TodoListControlViewModel UseAmbientLightSensor
{
get
{
return this.useAmbientLightSensor;
}
set
{
this.Set(ref this.useAmbientLightSensor, value);
}
}
The view model needs to extend from the ViewModelBase class which provides the Set method that raises the OnPropertyChanged event, allowing the view to know of any change in the view model.
For more info, check the INotifyPropertyChanged interface and its implementation.
Greatings, I'm creating a wpf user library control, which has a windows form control. Is possible pass values to properties class library control (not windows forms control properties)?, I have this:
WPF User Control Library (XAML):
<wfi:WindowsFormsHost Height="300" Name="winFormsHost" VerticalAlignment="Top" >
<wfr:ReportViewer x:Name="rptViewer" ProcessingMode="Remote"/>
</wfi:WindowsFormsHost>
....
WPF User Control Library (C#):
public partial class ReportViewer : UserControl
{
public static readonly DependencyProperty UrlReportServerProperty =
DependencyProperty.Register("UrlReportServer", typeof(string), typeof(ReportViewer),
new PropertyMetadata((string)""));
.... // Other Dependecies properties
public string UrlReportServer
{
get { return (string)GetValue(UrlReportServerProperty);}
set { SetValue(UrlReportServerProperty, value); }
}
............ // Other properties
public ReportViewer()
{
InitializeComponent();
this.DataContext = this;
ReportViewerLoad();
}
public void ReportViewerLoad()
{
rptViewer.ProcessingMode = ProcessingMode.Remote;
rptViewer.ServerReport.ReportServerUrl =
new Uri(UrlReportServer);
...... //Pass credentials to server reports and parameters to Report with Properties.
rptViewer.ServerReport.Refresh();
this.rptViewer.RefreshReport();
}
In WPF App, MainPage (XAML) with the reference library:
<WPFControlsSol:ReportViewer HorizontalAlignment="Left" Margin="0,0,0,0"
VerticalAlignment="Top" Width="644"
UrlReportServer="{Binding Url}"
</WPFControlsSol:ReportViewer>
WPF App, MainPage (C#):
public partial class MainPageView : Window
{
public MainPageView()
{
InitializeComponent();
ViewModel viewModel = new ViewModel();
DataContext = viewModel;
}
}
In ViewModel:
public class ViewModel : ViewModelBase
{
private string _url; .... // Other attributes
public string Url
{
get { return _url; }
set
{
if (_url != value)
{
_url = value;
RaisePropertyChanged("Url"); //Notification Method own MVVM Template I use.
}
}
} .... // Other properties
public ViewModel()
{
LoadReport();
}
public void LoadReport()
{
Url = "http://IPSERVER"; .... // Other properties
}
But This not works.
Use the EventHandler Delegate to publish and subscribe an event. WHen information is ready, raise the event and pass along the information required in the EventArgs
You are talking about the nested user controls problem. Catel provides and out of the box solution for you. Take a look at it as an example or just use it as the framework for your app, that is up to you.
Another great feature is that you can map properties between views and view models via easy attributes.
Searching the internet, I found a number of solutions for you. Please take a look at the following pages:
Walkthrough: Using ReportViewer in a WPF Application
Using Report Viewer Control in WPF
Using a Report Viewer Control in Windows Presentation Foundation (WPF)
Using MS ReportViewer in WPF contains a good tip
WindowsFormsHost.PropertyMap Property page on MSDN shows how to translate WPF control properties to WinForms properties and vice versa.
Pass parameters from WPF user control to Windows Form User Control via WindowsFormsHost
Integrate WPF UserControls in WinForms (The other way around, but still provides a valid method for you)
UPDATE >>>
I don't really understand your problem. If you really don't want to follow any advice from those links I gave you, just create a Windows Forms UserControl that hosts the ReportViewer control internally and declare all the properties that you need on that UserControl. Then use XAML like this:
<wfi:WindowsFormsHost Height="300" Name="winFormsHost" VerticalAlignment="Top" >
<YourWinFormsUserControlWithInternalReportViewer UrlServer="Something"
Path="Some/Path/Report.rdl" User="Geert" Password="password" />
</wfi:WindowsFormsHost>
I have a window which displays sales between a certain time in a restaurant/shop. When the user selects the time period to query, it shows sales data between that time. I am also Programatically creating a list of users which one can then select to filter a query. For example, I choose the 'Michael' user which is then used to show all sales that have been attributed to him (in the time frame previously selected).
Creating the ListView of users is fairly easy but I am trying to append this list with an item which would read 'All Users'. This would then be passed back to the query, which would then recognize this user by some Property (UserId = 999 or whatever. Not important) to populate the page with the data of all users again.
Right now I have to exit the page and go back in to do this. Not very elegant!
I was going to append a User object in the ViewModel to the list that is generated from the database EF but it creates a list of IUsers so I can't instantiate an actual instance of it (maybe I am being incredibly stupid here and am missing something fundamental?).
Any help in achieving this goal would be most appreciated.
Your UI would typically create a view model that wraps the underlying user information. Then you would have a collection of these view models, to which the view binds. Assuming you have that, it is a simple matter of adding a sentinel instance to this collection. It might look something like this:
// this is your DAL class
public class User
{
}
// a view model to wrap the DAL class
public class UserViewModel
{
// a special instance of the view model to represent all users
public static readonly UserViewModel AllUsers = new UserViewModel(null);
private readonly User user;
public UserViewModel(User user)
{
...
}
// view binds to this to display user
public string Name
{
get { return this.user == null ? "<<All>>" : this.user.Name; }
}
}
public class MainViewModel()
{
private readonly ICollection<UserViewModel> users;
public MainViewModel()
{
this.users = ...;
this.users.Add(UserViewModel.AllUsers);
}
public ICollection<UserViewModel> Users
{
...
}
}
In your code to construct the query, all you need to do is check whether the user in the user view model is present. If not, there is no need to append any user selection onto the query.
You can try to use CompositeCollection to set ItemSource of your ListBox -
<ListBox>
<ListBox.ItemsSource>
<CompositeCollection>
<CollectionContainer Collection="{Binding YourCollection}" />
<ListBoxItem Foreground="Magenta">Select All</ListBoxItem>
</CompositeCollection>
</ListBox.ItemsSource>
</ListBox>
But you will have to apply some workaround(like using BindingProxy) to make Binding work as CollectionContainer doesn't support bindings, refer these links -
http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/637b563f-8f2f-4af3-a7aa-5d96b719d5fd/
How do you bind a CollectionContainer to a collection in a view model?