Develop Reference

How to initialise WPF navigation bar on application start

I have a window with a FrameContent that I use to navigate between pages:
<Frame Name="FrameContent" VerticalAlignment="Stretch" Margin="0,34,-0.8,0.4" Grid.RowSpan="2"/>
It works great, but it only appears after I have already navigated to a page, where I would like to see it (even though back/forward will be greyed out) from the beginning.
MainWindow.xaml.cs
public MainWindow()
{
InitializeComponent();
FrameContent.Navigate(new HomeView());
}
I tried adding
ShowsNavigationUI="True"
Attribute to the HomeView page but it did nothing.
Does anyone know if this is possible?

Try adding NavigationUIVisibility="Visible", let me know if it works.

WPF user controls and name scoping

I've been playing around with WPF and MVVM and noticed a strange thing. When using {Binding ElementName=...} on a custom user control, the name of the root element within the user control seems to be visible in the window using the control. Say, here is an example user control:
<UserControl x:Class="TryWPF.EmployeeControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:TryWPF"
Name="root">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<TextBlock Grid.Column="0" Text="{Binding}"/>
<Button Grid.Column="1" Content="Delete"
Command="{Binding DeleteEmployee, ElementName=root}"
CommandParameter="{Binding}"/>
</Grid>
</UserControl>
Looks pretty legit to me. Now, the dependency property DeleteEmployee is defined in the code-behind, like this:
public partial class EmployeeControl : UserControl
{
public static DependencyProperty DeleteEmployeeProperty
= DependencyProperty.Register("DeleteEmployee",
typeof(ICommand),
typeof(EmployeeControl));
public EmployeeControl()
{
InitializeComponent();
}
public ICommand DeleteEmployee
{
get
{
return (ICommand)GetValue(DeleteEmployeeProperty);
}
set
{
SetValue(DeleteEmployeeProperty, value);
}
}
}
Nothing mysterious here. Then, the window using the control looks like this:
<Window x:Class="TryWPF.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:TryWPF"
Name="root"
Title="Try WPF!" Height="350" Width="525">
<StackPanel>
<ListBox ItemsSource="{Binding Employees}" HorizontalContentAlignment="Stretch">
<ListBox.ItemTemplate>
<DataTemplate>
<local:EmployeeControl
HorizontalAlignment="Stretch"
DeleteEmployee="{Binding DataContext.DeleteEmployee, ElementName=root}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</StackPanel>
</Window>
Again, nothing fancy... except the fact that both the window and the user control have the same name! But I'd expect root to mean the same thing throughout the whole window XAML file, and therefore refer to the window, not to the user control. Alas, the following message is printed when I run it:
System.Windows.Data Error: 40 : BindingExpression path error:
'DeleteEmployee' property not found on 'object' ''String'
(HashCode=-843597893)'.
BindingExpression:Path=DataContext.DeleteEmployee;
DataItem='EmployeeControl' (Name='root'); target element is
'EmployeeControl' (Name='root'); target property is 'DeleteEmployee'
(type 'ICommand')
DataItem='EmployeeControl' (Name='root') makes me think that it treats ElementName=root as referring to the control itself. The fact that it looks for DeleteEmployee on string confirms that suspicion because string is exactly what the data context is in my contrived VM. Here it is, for the sake of completeness:
class ViewModel
{
public ObservableCollection<string> Employees { get; private set; }
public ICommand DeleteEmployee { get; private set; }
public ViewModel()
{
Employees = new ObservableCollection<string>();
Employees.Add("e1");
Employees.Add("e2");
Employees.Add("e3");
DeleteEmployee = new DelegateCommand<string>(OnDeleteEmployee);
}
private void OnDeleteEmployee(string employee)
{
Employees.Remove(employee);
}
}
It is instantiated and assigned to the window in the constructor, which is the only thing in code-behind for the window:
public MainWindow()
{
InitializeComponent();
DataContext = new ViewModel();
}
This phenomenon prompts the following questions:
Is this by design?
If so, how is someone using a custom control supposed to know what name it uses internally?
If Name is not supposed to be used in custom control at all?
If so, then what are the alternatives? I switched to using {RelativeSource} in FindAncestor mode, which is working fine, but are there better ways?
Does this have anything to do with the fact that data templates define their own names copes? It doesn't stop me from referring to the main window from within a template if I just rename it so the name doesn't clash with the control.

Your confusion here about how wpf namescopes work is understanable in this situation.
Your issue is simply that you are applying a binding upon a UserControl, which is the "root" (so to speak) of its own namescope. UserControls, and pretty much any container objects, have their own namescopes. These scopes encompass not only child elements, but the object that contains the namescope as well. This is why you can apply x:Name="root" to your window and (except in this one case) locate it from a child control. If you couldn't, namescopes would be pretty much useless.
The confusion comes when you're acting upon a root of a namescope within an encompassing namescope. Your assumption was that the parent's namescope had precedence, but it does not. The Binding is calling FindName on the target object, which in your case is your user control. (Side note, the Binding isn't doing jack, the actual calls can be found in ElementObjectRef.GetObject, but that's where the Binding delegates the call to)
When you call FindName on the root of a namescope, only names defined within this scope are examined. Parent scopes are not searched. (Edit... a bit more reading of the source http://referencesource.microsoft.com/#PresentationFramework/src/Framework/MS/Internal/Data/ObjectRef.cs,5a01adbbb94284c0 starting at line 46 I see that the algorithm walks up the visual tree until it finds a target, so child scopes have precedence over parent scopes)
The result of all this is that you get the user control instance instead of the window, like you were hoping. Now, to answer your individual questions...
1. Is this by design?
Yep. Otherwise namescopes wouldn't work.
2. If so, how is someone using a custom control supposed to know what name it uses internally?
Ideally, you wouldn't. Just like you don't ever want to have to know the name of the root of a TextBox. Interestingly, though, knowing the names of templates defined within a control is often important when attempting to modify it's look and feel...
3. If Name is not supposed to be used in custom control at all?
If so, then what are the alternatives? I switched to using {RelativeSource} in FindAncestor mode, which is working fine, but are there better ways?
No! It's fine. Use it. If you aren't sharing your UserControl with other people, just make sure to change its name if you are experiencing this particular problem. If you aren't having any problem, reuse the same name all day, it isn't hurting anything.
If you ARE sharing your UserControl, you should probably rename it to something that won't conflict with other people's names. Call it MuhUserControlTypeName_MuhRoot_Durr or something.
4. If so, then what are the alternatives? I switched to using {RelativeSource} in FindAncestor mode, which is working fine, but are there better ways?
Nah. Just change the x:Name of your user control and move on.
5. Does this have anything to do with the fact that data templates define their own names copes? It doesn't stop me from referring to the main window from within a template if I just rename it so the name doesn't clash with the control.
No, I don't believe so. I don't think there is any good reason for it to be, anyhow.

WPF -- Binding Not Working

I'm having a rather frustrating problem here... I have a WPF Page that contains a TabControl, and the content of the various TabItems is another WPF Page (hosted in a Frame because Page can only have Frame or Window as a parent). Even though the FlowCalibrationSummaryView is being displayed, everything on it is empty because the data binding of the SummaryViewModel is not working for some reason. Here's part of the XAML:
<TabControl Grid.Row="0">
<TabItem Header="Current Calibration">
<TabItem.Content>
<Frame>
<Frame.Content>
<view:FlowCalibrationSummaryView DataContext="{Binding SummaryViewModel}"/>
</Frame.Content>
</Frame>
</TabItem.Content>
</TabItem>
</TabControl>
I have a break point on the get of SummaryViewModel, and it is only getting hit by the code that is constructing it in the parent view model. Here's the property being bound to:
public const string SummaryViewModelPropertyName = "SummaryViewModel";
private FlowCalibrationSummaryViewModel _SummaryViewModel;
public FlowCalibrationSummaryViewModel SummaryViewModel
{
get { return _SummaryViewModel; }
set
{
if (_SummaryViewModel == value)
return;
_SummaryViewModel = value;
RaisePropertyChanged(SummaryViewModelPropertyName);
}
}
At this point I'm completely stumped, I cannot for the life of me figure out why this binding is not working. Any help would be much appreciated.
Update: It definitely has something to do with it being in a Frame. I tried changing the FlowCalibrationSummaryView to a UserControl instead of a Page to see if that helped, and it didn't, then I tried taking it out of the Frame it was wrapped in and that worked. All of the views in my project are done as Pages so for consistency's sake I'd prefer this to be a Page, but then I have to host it in a Frame. Is there something I'm missing here, or is the proper usage to do it as a UserControl?

I would take a look at the answer provided in this question. It seems to provide a specific explanation of the behavior of Frame in this case.
Unless there is a specific reason you have chosen Frame over UserControl, you would be better off re-implementing this (and any other sub-view) as UserControl instead.

ContentControl is not visible when application starts via UI Automation test, but its visible when application starts by user

We are using the prism and WPF to build application. Recently we started using UI Automation (UIA) to test our app. But some strange behavior occurred when we run UIA test. Here's simplified shell:
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TextBlock
Grid.Row="0" Grid.Column="0"
Name="loadingProgressText"
VerticalAlignment="Center" HorizontalAlignment="Center"
Text="Loading, please wait..."/>
<Border
Grid.Row="0"
x:Name="MainViewArea">
<Grid>
...
</Grid>
</Border>
<!-- Popup -->
<ContentControl
x:Name="PopupContentControl"
Grid.Row="0"
prism:RegionManager.RegionName="PopupRegion"
Focusable="False">
</ContentControl>
<!-- ErrorPopup -->
<ContentControl
x:Name="ErrorContentControl"
Grid.Row="0"
prism:RegionManager.RegionName="ErrorRegion"
Focusable="False">
</ContentControl>
</Grid>
In our app, we use layers (Popup and ErrorPopup) to hide MainViewArea, to deny access to the controls. To show Popup, we use next method:
//In constructor of current ViewModel we store _popupRegion instance to the local variable:
_popupRegion = _regionManager.Regions["PopupRegion"];
//---
private readonly Stack<UserControl> _popups = new Stack<UserControl>();
public void ShowPopup(UserControl popup)
{
_popups.Push(popup);
_popupRegion.Add(PopupView);
_popupRegion.Activate(PopupView);
}
public UserControl PopupView
{
get
{
if (_popups.Any())
return _popups.Peek();
return null;
}
}
Similar to this, we show ErrorPopup over all elements of our application:
// In constructor we store _errorRegion:
_errorRegion = _regionManager.Regions["ErrorRegion"]
// ---
private UserControl _error_popup;
public void ShowError(UserControl popup)
{
if (_error_popup == null)
{
_error_popup = popup;
_errorRegion.Add(_error_popup);
_errorRegion.Activate(_error_popup);
}
}
Mistics...
When we run it as users do it (double click on app icon), we can see both custom controls (using AutomationElement.FindFirst method, or through Visual UI Automation Verify). But when we start it using UI Automation test - ErrorPopup disapears from the tree of the controls. We trying to start the application like this:
System.Diagnostics.Process.Start(pathToExeFile);
I think that we missed something. But what?
Edit #1
As #chrismead said, we tried to run our app with UseShellExecute flag set to true, but this does not help. But if we start app from cmd line, and manually click the button, Popup and ErrorPopup are visible in automation controls tree.
Thread appThread = new Thread(delegate()
{
_userAppProcess = new Process();
_userAppProcess.StartInfo.FileName = pathToExeFile;
_userAppProcess.StartInfo.WorkingDirectory = System.IO.Directory.GetCurrentDirectory();
_userAppProcess.StartInfo.UseShellExecute = true;
_userAppProcess.Start();
});
appThread.SetApartmentState(ApartmentState.STA);
appThread.Start();
One of our suggestion is when we use method FindAll or FindFirst to search the button to click, window somehow cached its UI Automation state, and does not update it.
Edit #2
We have find, that extension method of prism library IRegionManager.RegisterViewWithRegion(RegionNames.OurRegion, typeof(Views.OurView)) have some strange behavior. If we stopped use it, this solve our problem particulary. Now we able to see ErrorView and any kind of view in PopupContentControl, and application updates UIA elements tree structure. But this is not an answer - "Just stop use this feature"!
In MainViewArea we have a ContentControl, which updates it content depending on user actions, and we are able to see only the first loaded UserControl to that ContentControl.Content property. This is performed like this:
IRegionManager regionManager = Container.Resolve<IRegionManager>();
regionManager.RequestNavigate(RegionNames.MainContentRegion, this.Uri);
And if we change the view, no updates will performed in UI Automation tree - the first loaded view will be in it instead. But visually we observe another View, and WPFInspector shows it properly (its show not a UI Automation tree), but Inspect.exe - not.
Also our suggestion that window use some kind of caching is wrong - caching in UI Automation client we have to turn on explicitly, but we don't do it.

I'm sorry that I've missed some detail, that was the key to the answer. I think that it was not important thing. Anyway.
We used NavBar from DevExpress controls library for WPF. What turns out, is when NavBar is present, dynamically created views are not appears on the UI Automation tree. When remove it from the window, there was an ability to see all dynamically loaded views. What does the NavBar - still mistic for me.
Here bright example to see what happened, if NavBar is present or absent on the Window (DevExpress is required).
MainWindow.xaml:
<Window xmlns:dxn="http://schemas.devexpress.com/winfx/2008/xaml/navbar"
x:Class="Test.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525"
>
<Grid Name="ContentGrid">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition></RowDefinition>
<RowDefinition></RowDefinition>
</Grid.RowDefinitions>
<!--Comment NavBar to see dynamic control in UI Automation tree-->
<dxn:NavBarControl Name="asdasd">
<dxn:NavBarControl.Groups>
<dxn:NavBarGroup Header="asdasdasdasd" />
</dxn:NavBarControl.Groups>
</dxn:NavBarControl>
<TextBox Grid.Column="1" Name="Statictb" Text="static is visible in ui automation tree" />
<Button Grid.Row="1" Content="Create controls" Height="25" Click="Button_Click"/>
</Grid>
</Window>
MainWindow.xaml.cs
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
TextBox tb = new TextBox();
Grid.SetRow(tb, 1);
Grid.SetColumn(tb, 1);
tb.Text = "dynamic is not visible, if NavBar here...";
ContentGrid.Children.Add(tb);
}
}
Edit
According to the DevExpress answer on their support site:
After a peer is created, listening of automation events may cause performance issues. We have decided to clear invocation lists of automation events to resolve it. In your specific situation, you need to disabling clearing. To do it, please set the static DevExpress.Xpf.Core.ClearAutomationEventsHelper.IsEnabled property to False in the Window constructor.
This solve the problem.

My guess is that the ContentControl's automation peer should update its children with AutomationPeer.ResetChildrenCache() after the view has been changed.
AutomationPeer.InvalidatePeer() should have the same effect (in addition to other side effects) and it is supposed to be called automatically in response to the LayoutUpdated event. You might want to check that the LayoutUpdated event is raised when the view changes.

stukselbax, try to find a sequence of keystrokes (TABs, and an ENTER most likely) to click the button that enables you to see the items. it is pretty easy to send keystrokes and i can add more in here about that if that works for you. you can always establish a tab order in your application that makes the most sense for users.
------ Update on 6/20/12 --------
Have you tried double clicking a shortcut to your app on the desktop using PInvoke to see if you can see the controls when it is opened that way? Here is a link to an example here on stackoverflow:
Directing mouse events [DllImport("user32.dll")] click, double click
Another idea: some of the controls on the app I am currently automating don't show up in the tree until a mouse click occurs on them. To accomplish this without using any hardcoded coordinates, I find something in the tree which is just (above/below/etc) the place where I need to click to get the control to appear. I then get the mouse coordinates for that item and put the mouse at a small offset from there and click. Then I can find my controls in the tree. If the app is resized, moved around, etc. this will still work since the small offset is still valid.

Frame ViewModel

I would like information on how to load a Frame through a viewmodel. I know how to load through the code-behind, but now want to move everything to the ViewModel linking frame.content or other property of binding to a Frame.
Do you have tips or suggestions?

My answer is a bit off subject, cause I'm taking a leap here on what you are really trying to accomplish.
If you are looking for navigation implementation, you might consider other approaches.
Use Prism's Navigation feature, the RegionManager abstracts enough that you can just use it in your VM and navigate to a Uri.
Use a TabControl that you can strip out the headers with a simple style. Now you can bind the TabControl SelectedItem to the VM, imagine every tab is a view (or a VM) you can now control navigation with a matter of switching tabs.
HTH
Ariel

Bind the contents of the frame to a Page object
<Page>
<Viewbox Stretch="Fill" Margin="15">
<Frame Height="800" Width="1280" Content="{Binding SlideFrame}"/>
</Viewbox>
</Page>
using System.Windows.Controls;
private Page _slideFrame;
// Property
public Page SlideFrame
{
get { return _slideFrame; }
set
{
_slideFrame = value;
NotifyPropertyChanged("SlideFrame");
}
}