Develop Reference

WPF Button disables itself without binding or code making it so

I'll give some details below, but briefly I have a problem wherein a button in my WPF application will disable itself if I click somewhere else in the application. This button is linked to a Command but there is absolutely NOTHING bound to the IsEnabled property of the button and the Command CanExecute callback just sets e.CanExecute to true.
I saw this similar SO question (Weird problem where Button does not get re-enabled unless the mouse is clicked) but it was not helpful.
The application is simple and consists of a DockPanel divided into 4 parts. The left section contains a DataGrid and the right section contains a UserControl that also contains a couple DataGrids as well as the offending Button. It's so weird, but if I click on any row in the left DataGrid, the Button in the right section becomes disabled. The only way I can then re-enable it is to click on any row in either of the DataGrids in the right section!
Again, there IS absolutely nothing bound to the IsEnabled property of the button or any other code/markup implicitly in place that would allow this to happen.
Some relevant code snippets:
UserControl Command bindings:
<UserControl.CommandBindings>
<CommandBinding Command="cmd:DBScriptCommands.LoadScripts" CanExecute="cmdLoadScripts_CanExecute" Executed="cmdLoadScripts_Executed" />
<CommandBinding Command="cmd:DBScriptCommands.RunScripts" CanExecute="cmdRunScripts_CanExecute" Executed="cmdRunScripts_Executed" />
</UserControl.CommandBindings>
Button xaml:
<Button IsEnabled="True" x:Name="btnLoadScripts" Command="cmd:DBScriptCommands.LoadScripts">
<StackPanel HorizontalAlignment="Stretch">
<Image Source="/Images/folder-open.png" />
<TextBlock>Load Scripts</TextBlock>
</StackPanel>
</Button>
CanExecute for Command:
private void cmdLoadScripts_CanExecute(object sender, CanExecuteRoutedEventArgs e)
{
e.CanExecute = true;
}
This has me baffled and any ideas are appreciated. If more information is needed, please let me know.
Edit 1:
Seems like it is something to do with the Command (still not sure what) - if I remove the Command parameter from the Button, the problem goes away - not useful because I want the button to trigger the Command, but interesting. In the CanExecute(), if I set e.CanExecute to false, the button is always disabled which makes sense. When it is set to true (like it is now) then I have the problem I've describe where it seems like something is setting it to false by magic sometimes.
Thanks

How do I make screen readers read my WPF message similarly to how they read Win32 MessageBox?

We have a WPF desktop application which needs to show some custom message windows. I am having trouble getting them to be read aloud properly by screen readers such as JAWS from Freedom Scientific.
I want to achieve the same behavior as when showing a system message box. For comparison, System.Windows.MessageBox.Show("my message", "My Caption); is announced by JAWS as "My caption dialog. My message. OK Button". This is perfect.
When my message windows are opened (containing only a TextBlock and OK Button), the window title is announced and the OK button is announced as having focus but the TextBlock message is not announced.
Here's a simple test application which shows the issue. Our real app has icons and other status text, of course.
<Window x:Class="Jaws_MessageBox_Test.MyMessageBox"
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:Jaws_MessageBox_Test"
mc:Ignorable="d"
Title="MyMessageBox" Height="300" Width="300">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="*"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
</Grid.RowDefinitions>
<TextBlock x:Name="mainLabel" Grid.Row="0">Hi there, this is a test to see if JAWS will read the main textbloc when shown.</TextBlock>
<Button Grid.Row="1" Margin="5" HorizontalAlignment="Right" Padding="10,0,10,0" IsDefault="True" x:Name="closeButton" Click="closeButton_Click">_Close</Button>
</Grid>
</Window>
When I show this using:
var mb = new MyMessageBox();
mb.ShowDialog();
The screen reader announces: "MyMessageBox. Close Button" so it's not reading the TextBlock like the system message box does.
What I've found using the Windows SDK inspect and accevent tools is that
The system message box accessibility type is 'Dialog' but the WPF dialog's accessibility type is 'Window'. This might matter. There is no UI Automation Control Type of Dialog https://msdn.microsoft.com/en-us/library/ms749005(v=vs.110).aspx . Is this a bug or limitation in WPF perhaps?
I have tried setting various 'AutomationProperties' attached properties on my window so that the AutomationPeer will have better info but none of those are read when the ShowDialog runs.
Since TextBlock cannot receive input focus, there's no way to even get the text read by tabbing. I temporarily use a read-only TextBox instead to get focus but the experience is still wrong and our blind users should not have to tab around just to have a simple status message read to them.
As part of the experimenting, I also tried creating my own derived AutomationPeer for the message window but none of the Core method content is read automatically when the dialog is launched. The automation child list does have the title bar object listed as the first child whereas that's the last child for the system message box though I don't see a way to change that right now.
I'd greatly appreciate any help for creating a WPF-based custommessage box with full, proper accessibility for blind users.

You have to tell the automation API that your Window is a MessageBox.
To do that add this code to your Window
protected override AutomationPeer OnCreateAutomationPeer()
{
return new MessageBoxWindowAutomationPeer(this);
}
and add this class to your project
public class MessageBoxWindowAutomationPeer : WindowAutomationPeer
{
private const string WC_DIALOG = "#32770";
public MessageBoxWindowAutomationPeer(Window owner)
: base(owner)
{
}
protected override string GetClassNameCore()
{
return WC_DIALOG;
}
protected override string GetLocalizedControlTypeCore()
{
return "Dialogfeld";
}
protected override bool IsContentElementCore()
{
return true;
}
protected override bool IsControlElementCore()
{
return true;
}
}
As we don't need localization in our app "DialogFeld" is the german localized control type. Localizing that one is the part you would have to find out by yourself. ;-)

Set the AutomationProperties.HelpText on the run inside the Textblock
So for Example:
<TextBlock>
<Run Text="aTextString" AutomationProperties.HelpText="ATextString"/>
</TextBlock>
or
<TextBlock>
<Run Text="aTextString" AutomationProperties.HelpText="{Binding Text, RelativeSource={RelativeSource self}}"/>
</TextBlock>

OK from reading around the problem is with Jaws not WPF, as it tends not to read static text on Labels and TextBlocks - strange behaviour.
A workaround might be to use a TextBox, set the BorderStyle = None and place a rectangle on top of it, with fill = White, Opacity = 0.01. This will stop the user being able to focus on the TextBox and means the text will not be static and Jaws should read the text automatically . . .

One thing, does it have to be Jaws that reads the Dialogs that your App pops up?
Have you looked at using system.speech.synthesis.speechsynthesizer to speak the text when the dialog pops up - just a thought!

I don't know if this is correct solution but this works as required on JAWS 18.
<Window ...>
<UserControl>
<StackPanel>
<TextBlock Name="MessageText" ... />
<Button Name="OKButton" ...../>
</StackPanel>
</UserControl>
</Window>
and then focusing the button when window is loaded.
So I wrapped stackpanel inside the usercontrol element.

WPF - Clicking a button resets some TabControl tabs

I'm using Caliburn.Micro as a MVVM framework and I have an app that has a TabControl and each Tab is a ViewModel (and View) that has a couple of buttons on it and a custom UserControl I built, that also has a button in it. All of the tabs have the same structure (they use the same ViewModel/View).
The problem is that, for some reason, when I click the button inside the custom UserControl, that resets other Tabs - the controls inside reset to their initial values, DataGrids get cleared etc. The weird thing about this is that:
it doesn't happen always, it doesn't always happen to all tabs AND it happens even if I comment out everything within the UserControl's button's Click event (so just by the Click event being raised, some and sometimes all tabs just reset for no reason).
I've read that TabControl has this weird thing where it doesn't persist data in some cases, but
a) I don't think this is the case, because the data persists fine when switching between tabs, it just disappears when I click the button
b) Even if it is the same issue, I can't really use the solutions provided by Google, because the binding of Views, ViewModels and the TabControl is done by Caliburn.Micro and I can't mess around with how it does that (so, for example, I can't make the TabControl use a new property instead of ItemSource as some posts suggest).
It looks like it just completely resets the whole view just as if the app was just launched. When I read about the persistence issues of TabControl, people usually meant that things like sorting settings, selections get cleared, but in this case the whole tab clears including the data of DataGrids and everything else. I noticed that it only re-creates the views (their constructors get called when switching back to their tabs), but the ViewModels behind the views don't!
Has anyone else experienced this before? What did you do?

I had been searching for hours and somehow completely missed this solution: Stop TabControl from recreating its children
I'm not really sure how it works, but it somehow stops the Views from getting re-created when switching tabs and pressing any buttons.

One Solution maybe to avoid using TabItems to hold your controls. Instead leave the TabItems empty, and add all of the controls that normally would go in a TabItems into the same grid element and set the Panel.ZIndex higher for the control that you want on top. Example:
<Window x:Class="testtab.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="testtab" Height="300" Width="300"
>
<Grid Name="Grid1">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Label Grid.Row="0" Content="Persistant State for UserControls"
Background="Blue" Foreground="Yellow"/>
<TabControl Grid.Row="1"
Name="TabControl1"
SelectionChanged="TabControl_SelectionChanged">
<TabItem Header="Page1" />
<TabItem Header="Page2" />
<TabItem Header="Page3" />
</TabControl>
<!-- ZIndex: top=1; botton=0 -->
<TextBox Name="b1" Grid.Row="2" Panel.ZIndex="1" Text="b1"/>
<TextBox Name="b2" Grid.Row="2" Panel.ZIndex="0" Text="b2"/>
<TextBox Name="b3" Grid.Row="2" Panel.ZIndex="0" Text="b3"/>
</Grid>
</Window>
Here's the related event handler:
void TabControl_SelectionChanged(
object sender,
SelectionChangedEventArgs e)
{
//need this if settings SelectedIndex on TabControl
if (!IsInitialized) return;
switch(TabControl1.SelectedIndex) {
case 0:
Panel.SetZIndex(b1, 1);
Panel.SetZIndex(b2, 0);
Panel.SetZIndex(b3, 0);
break;
case 1:
Panel.SetZIndex(b1, 0);
Panel.SetZIndex(b2, 1);
Panel.SetZIndex(b3, 0);
break;
case 2:
Panel.SetZIndex(b1, 0);
Panel.SetZIndex(b2, 0);
Panel.SetZIndex(b3, 1);
break;
}
e.Handled = true;
}
I don't have any UserControls handy... so We are using TextBox controls...
One Afterthought, You might need too also control the Visibility property for each control selecting between "Collapsed" and "Visible". In other words, if the control is not shown because its tab is not selected, then its Visibility should be set to collapsed or hidden so as not to interfere with the tab that is on top.

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.

Attach a single close button on the tabcontrol in C#

How i can attach a single close button on the tabcontrol in C#.
There is a many way to attach a close button individually on each tabpages but I want to attach only single(e.g.) we can see on microsoft visual stdio 2008.
So Plz help me.

Here is a cheap way to do it, which might get you started:
<Window x:Class="WpfApplication1.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">
<DockPanel>
<TabControl DockPanel.Dock="Top">
<TabItem Header="Test1" />
<TabItem Header="Test2" />
<TabItem Header="Test3" />
<TabItem Focusable="False">
<TabItem.Header>
<Button Command="{Binding CloseTab}" Content="X" Width="21" HorizontalAlignment="Stretch" />
</TabItem.Header>
</TabItem>
</TabControl>
</DockPanel>
</Window>
You then are left to implement a public ICommand CloseTab field or property on your DataContext, and style the tab control to your liking.
Edit:
If you use this method:
Wiring up the button is tricky. You have to be careful not to close the tab that contains the button
This isn't well adapted to dynamically created tabs, because you have to ensure the close button is appended to the list
You have to figure out how to re-select the last selected tab, when you close the selected tab
You'll also have weird behavior when tabs start to wrap
The tab-stop behavior is hard to get right. You can't make the last TabItem focusable, since focus is used to determine what to close, but tabbing to the close button breaks the normal TabItem keyboard flow
I have come up with a style that makes the button look like a regular tab, with a bold X on it, which makes it visually more like IE8, and fixes the keyboard selection problem. But it is complicated, and this solution is complicated enough.
Ultimately, a close button on every tab jives better with the tab control's default behavior. The only problem with that solution is that it takes up more space. You could cheat and make the close button collapse until you mouse over the tab item, though that's sort of a user-experience no-no, unless you just shrink it.
If you are serious about following through with the separate close button, I suggest you look at this article, and adapt what they do for the scroll buttons to your close button:
http://www.blogs.intuidev.com/post/2010/02/10/TabControlStyling_PartThree.aspx
Ignore what they do for close buttons :)

Would it be possible to have your tabcontrol on another container control and let that control's close button do the job?