I'm sorry for this being so wordy, but I want to make the situation perfectly clear. Please, if you are a WPF pro, take a look.
There are two CollectionViewSource bound to ItemsControls that use UserControl Views to display either StackPanels or custom Buttons. There is one for each side shown in the screenshot below. The problem I'm encountering is that when the parent collection property is set, all of the buttons in the DataTemplate view are disabled. Even the 2 buttons higher up are having the same problem even though they worked before my recent edits.
If I click on the form, or press any key, the buttons enable. As soon as the property is reset to a newly edited and sorted collection, they disable again. Rinse and repeat. This is what it looks like. The first frame is how it starts (gray using StackPanel), the 2nd is what it looks like when the RFS button is clicked, and the 3rd frame is what happens when I click anywhere or press a key.
I've been going in circles trying out things. The only thing that seems to work is a code-behind workaround that sets focus to one thing and then back. However, that would not be good for the user if they are trying to use one of the other dashboard items.
Since the WPF for all of this is very massive, I'll try to include just the relevant parts. These are the ItemsControls on the TabItemControl (UserControl).
<!-- BID (SELL) DEPTH -->
<ItemsControl Grid.Row="0" Grid.Column="0" x:Name="bidDepthList" ItemsSource="{Binding Source={StaticResource BidDepthCollection}}"
Visibility="{Binding Path=IsMultilegEnabled, Converter={StaticResource CollapsedConverter}}">
<ItemsControl.ItemTemplate>
<DataTemplate DataType="{x:Type viewmodels:DepthLevelViewModel}">
<v:DepthLevelRowView x:Name="BidDepthLevelRowViewControl" DataContext="{Binding}" HorizontalAlignment="Center" Margin="1,0,1,3" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
<!-- ASK (BUY) DEPTH -->
<ItemsControl Grid.Row="0" Grid.Column="1" x:Name="askDepthList" ItemsSource="{Binding Source={StaticResource AskDepthCollection}}"
Visibility="{Binding Path=IsMultilegEnabled, Converter={StaticResource CollapsedConverter}}">
<ItemsControl.ItemTemplate>
<DataTemplate DataType="{x:Type viewmodels:DepthLevelViewModel}">
<v:DepthLevelRowView x:Name="AskDepthLevelRowViewControl" DataContext="{Binding}" HorizontalAlignment="Center" Margin="1,0,1,3" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
The view being used has 4 "controls" inside of a grid. Only one of them is displayed at a time depending on the state (RFS OFF/RFS ON) and which side they are on (Sell/Buy). The others are collapsed. As you can see, this is fine.
The only common factor between them is that they have their Command set, as do most of the controls at the top that are disabling/enabling correctly. The fact that the buttons enable correctly if any mouse or keyboard action is taken tells me that the CanExecute handler is working, just not immediately. The other controls started working after I made these changes, but then the big buttons started misbehaving like the depth buttons have been doing.
I've tried using CommandManager.InvalidateRequerySuggested(); after altering the collections, but that didn't help.
NOTE: This is also happening even for something as simple as this:
<Button x:Name="TestBuyButton" Command="{x:Static ptcommands:OrderCommands.Buy}" CommandTarget="{Binding RelativeSource={RelativeSource Self}}" Content="Test Buy" />
I know the booleans are set correctly because I added test CheckBoxes to display the current value with IsChecked. And, they all enable, including the extremely basic Button, as soon as any input action is taken.
Is there something else I'm missing or a different approach I can take?
EDIT: I ended up using the Dispatcher to invoke my display update routine from the event thread over to the UI thread. The boolean values get set, but WPF still didn't requery the Command. BUT.. the CommandManager.InvalidateRequerySuggested() call then worked! The only thing I don't like about that is it sounds like a broadcast invalidation. I don't want all commands to be requeried. I just want the Buy and Sell commands to requery. I've tried all sorts of weirdness trying to get just those to work, but nothing has worked so far other than the global.
EDIT 2: It appears as though the InvalidateRequerySuggested is the way to go.
From MSDN CommandManager.InvalidateRequerySuggested:
The CommandManager only pays attention to certain conditions in determining when the command target has changed, such as change in keyboard focus. In situations where the CommandManager does not sufficiently determine a change in conditions that cause a command to not be able to execute, InvalidateRequerySuggested can be called to force the CommandManager to raise the RequerySuggested event.
This would explain why the focus changes and keypresses would cause the buttons to enable. The page also shows putting the call in a timer. Because of this, I assume it is not as resource intensive as I thought. So, I guess it's my permanent solution.
I had to make a few changes to get the buttons to enable without focus changes.
The boolean values were being set within a method called from an event thread. I had tried calling CommandManager.InvalidateRequerySuggested along with it, but nothing happened. Eventually I thought it might have something to do with the thread. This is what ended up resolving it.
In the parent form that the tab manager class (containing the event handlers and other logic) has access to, I added an invoke method:
Public Sub InvokeOnUiThread(ByRef uiAction As Action, Optional ByRef doAsync As Boolean = False)
Dim dispatchObject As Dispatcher = orderTicketView.Dispatcher
If (dispatchObject Is Nothing OrElse dispatchObject.CheckAccess()) Then
uiAction()
Else
If doAsync Then
dispatchObject.BeginInvoke(uiAction, DispatcherPriority.Normal)
Else
dispatchObject.Invoke(uiAction, DispatcherPriority.Normal)
End If
End If
End Sub
In the tab manager event handler, I changed it to call the update routine through the invoker:
formOrderTicketView.InvokeOnUiThread(New Action(AddressOf UpdateButtons))
At the bottom of the UpdateButtons method, I added a call to the CommandManager if a change has been made that would require a requery:
CommandManager.InvalidateRequerySuggested()
I do not know what type of performance hit this would have, but apparently WPF executes it in its own way when focus changes and such. Calling it directly is the advised way to force it.
From MSDN CommandManager.InvalidateRequerySuggested:
The CommandManager only pays attention to certain conditions in determining when the command target has changed, such as change in keyboard focus. In situations where the CommandManager does not sufficiently determine a change in conditions that cause a command to not be able to execute, InvalidateRequerySuggested can be called to force the CommandManager to raise the RequerySuggested event.
Since it is working now, I am taking this as the resolution.
The command that's bound to the button...is there a CanExecute delegate with it? If so, you have to raise CanExecuteChanged when that delegate should be re-evaluated. Also, make sure the implementation of CanExecute isn't broken and incorrectly returning false;
Related
We are building a WPF application containing a DataGrid, which should call a function on the currently selected row if that row is double-clicked. We are aiming for an MVVM approach where possible, trying to avoid events.
Because I've done something similar for a DataGrid in a previous application, I thought this would work:
<DataGrid.InputBindings>
<MouseBinding MouseAction="LeftDoubleClick" Command="{Binding ShowDetailsCommand}"/>
</DataGrid.InputBindings>
In this working application, ShowDetailsCommand points to a method which accesses the currently selected DataGrid item via a data binding to SelectedItem.
Trying this same approach in the new project does not seem to work at all. The method which the command points to is never called (tested with a breakpoint and console output), and there is also no error message about the command not being found in the DataContext. We have also tried to move the <InputBindings> block directly into the Window object just to test if the DataContext may have changed further down, but double-clicking still produced no reaction.
As far as I can tell, the only major differences between the two DataGrids are:
The old one's ItemsSource was manually bound to a collection of objects, while the new one's Binding was created by dragging a DataSet onto it in the designer
The DataContext for the old project was a separate ViewModel class, while the new one's is the window's own Codebehind class (DataContext="{Binding RelativeSource={RelativeSource Mode=Self}}", declared on the Window)
Could either of these be the cause for an InputBinding not working? If not, is there anything else we could be doing wrong? Apologies if this is not enough information, I am just very unsure where the problem might be. I will try to supply more information about the code if needed.
Try to bind to the ShowDetailsCommand of the DataContext of the parent window using a RelativeSource:
Command="{Binding DataContext.ShowDetailsCommand,
RelativeSource={RelativeSource AncestorType=Window}}"
I have the following code that adds a context menu to a textbox on the UI. The user is supposed to be able to bring up the context menu and select a new units to be used. So the method CurrentUnits in my view model is bound to the textbox. I want a context menu populated by all the potential units. So the method Units in my view model returns a string[] of unit options; such as inches, cm, feet, meters, etc. When the user selects one the method NewUnits_Click is invoked. All works fine, however the contextmenu does not go away when the user selects a menu option. Pressing somewhere else on the screen like the application menu bar will then clear it. Has anyone else seen this problem, or see something wrong with the code below. It seems to have something to do with the ItemTemplate/DataTemplate I have, as creating an set of menu items by hand works fine.
<TextBlock Width="100" Text="{Binding CurrentUnits}" TextAlignment="Right">
<toolkit:ContextMenuService.ContextMenu>
<toolkit:ContextMenu ItemsSource="{Binding Units}">
<toolkit:ContextMenu.ItemTemplate>
<DataTemplate>
<toolkit:MenuItem Header="{Binding}" Click="NewUnits_Click" />
</DataTemplate>
</toolkit:ContextMenu.ItemTemplate>
</toolkit:ContextMenu>
</toolkit:ContextMenuService.ContextMenu>
</TextBlock>
If you aren't using MVVM when working with WPF, I highly suggest you to start doing so. And even if you are not, I suggest that instead of binding to Click you instead bind on the Command property which wants something that implements ICommand. I think that the behavior you are getting is intended, buttons and menu items in WPF are intended to bind to Commands, it's not just WinForms 2.0.
Another solution would be to hide the Context menu in the code-behind. Perhaps this resource will help you in achieving that.
I have a boolean property in my ViewModel, named lets say IsNotSupported that is used to show some warning information if a sensor is not supported. Therefore I use a BooleanToVisibilityConverter, that is added in the ressources:
<phone:PhoneApplicationPage.Resources>
<local:BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" />
</phone:PhoneApplicationPage.Resources>
and bind it to the stackpanel containing the warning:
<StackPanel x:Name="NotSupportedWarning" Visibility="{Binding IsNotSupported,
Converter={StaticResource BooleanToVisibilityConverter}}">
That works all quite well, but when loading the page, and the sensor is supported, the warning appears for just a fraction of a second and disappears afterwards. I know that this flickering is caused by the binding not having happened yet and therefore defaulting to visible.
That flicker it is annoying as hell... It should rather default to collapsed and be made visible only after it is clear that the warning should be shown. Also, this would avoid a second layouting pass after the binding and could therefore have positive performance impacts.
I had this problem over and over, and found nothing about it in the internet until I found this SO question, that is closely related, but is not found if searched for windows phone instead of silverlight. Both the problem and the solution might seem simple, but I really bugged me quite a long time, so I thought it might be a good idea to write a Q&A-style question about it to help others that are facing the same issue.
The solution is simple after you have seen it. You can control the default value of the binding (if the binding didnt happen yet) with FallbackValue. Your stackpanel XAML would look like:
<StackPanel x:Name="NotSupportedWarning" Visibility="{Binding IsNotSupported,
FallbackValue=Collapsed,
Converter={StaticResource BooleanToVisibilityConverter}}">
This way you get rid of the flicker and it does not have to be relayouted after the binding, if the warning stays hidden.
you can bind directly to a Visibility type of property instead of boolean and keep that property to collapsed by default plus you can implement INotifyPropertyChanged
FINAL NOTE
Final solution found in another post
Although I appreciated the clarification that was provided, the ultimate solution was in-fact provided by another solution as linked above. No matter WHAT I tried, the binding via the "Element Name" component was not working. I had to go based on the "Relative" hierarchy up the datagrid...
<Button Name="btnPrintReport"
Command="{Binding DataContext.MyPrintCommand,
RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type DataGrid}}}"
CommandParameter="{Binding}"
Height="16" Width="16" HorizontalAlignment="Center" >
<Image Source="MyButtonImage.png" IsHitTestVisible="True"/>
</Button>
Hope something not too complicated in WPF / MVVM environment. Here's the scenario.
I have a Window (.xaml) and a corresponding View Model (.cs). The form displays fine with all the data bindings no problem. (note: this is NOT done via any commercial "framework" )
One of the controls that is in the view window is a custom user control of a datagrid with all pre-defined columns, headings and content to be displayed when the view is shown. This works all no problem even though the control is not directly "defined" in the main window .xaml file, but just dropped on the form as the user control itself (which has its own obvious .cs code-behind).
With the main window's "DataContext" pointing to the View Model, and the user control that has a datagrid
<DataGrid AutoGenerateColumns="False"
Name="dataMyStuff"
ItemsSource="{Binding Path=MyTablePropertyOnViewModel,
NotifyOnSourceUpdated=True,
NotifyOnTargetUpdated=True}" ... />
Now, what I'm looking for. On this data grid, I have a column that has an image in the first column. When I click on this image, I want to print a report specific to the record as represented by this row (it has a PK value I use). So, how do I tell the image "KeyUp" event to go to the View Model event handler since that is where the data is, and some other methods I'll need for preparing the call to the report. The view portion of the grid is for cosmetic display to the user, and thus no "functionality" directly in this control.
-- EDIT -- per progress from answers
I've adjusted my datagrid per comments from Josh and Rachel, however, something still does not appear to be quite right... Seeing the button was using a "Command" instance, I interpreted this as it needed to attach to an instance of an "ICommand" interface object on my view model. So, I created an instance. I know the command handler works as it is also used for common things like Add, Edit, Save, Cancel, Exit, etc... So I have a new one for this printing purpose. For simplicity, I have it created as an Always Execute, so there is no method to handle the "CanExecute" portion of the control. I've set the button's "Command" to almost all iterations I could think of an still nothing, but here's an update of what I'm seeing going on.
<UserControl>
<Data grid columns / template, etc to the button>
<DataTemplate>
<Button Name="btnPrintReport"
Command="{Binding DataContext.MyPrintCommand}" >
<Image Source="myPrintImage.png"/>
</Button>
</DataTemplate>
</Data grid columns, etc>
</UserControl>
In my ViewModel class (myICommandButtonHandler inherits from ICommand)
private myICommandButtonHandler myPrintCommand;
public myICommandButtonHandler MyPrintCommand
{
get { if (myPrintCommand == null)
myPrintCommand = new myICommandButtonHandler(myPrint);
return myPrintCommand;
}
}
private void myPrint()
{
MessageBox.Show( "Doing the print job..." );
}
Now, what I'm seeing. During step through initialization of all the controls and such. I click menu item to call my Window to be displayed. FIRST, it creates an instance of the View Model controller. THEN, it calls the Window and passes in the View Model controller as parameter so it is immediately set at the Window level as the "DataContext" of the window. The main window then goes into it's "InitializeComponents" call and starts to build out all the other controls embedded, including this separate class that contains the data grid in question. At the constructor of this usercontrol (that has the datagrid), there is no "data context" set yet as the rest of the controls have not been initialized yet, and I don't know why / when the "bindings" apparently get "hooked" in. So, it appears that trying to do the binding to the data grid's command button are failing. HOWEVER, at run-time, the actual data IS updated in the grid, so I know that much is working.
So, the data grid has its "ItemsSource" set to a property of a "DataView" property on the view model, but the binding of the "button" doesn't appear to see the "MyPrintCommand" handler that I thought would get the hit.. and its action is to just display a message box (for now).
Usually I use an AttachedCommand Behavior which allows me to bind Events to ViewModel Commands. For example, you could use
<Image ...
local:CommandBehavior.Event="KeyUp"
local:CommandBehavior.Command="{Binding DataContext.PrintCommand, ElementName=dataMyStuff}"
local:CommandBehavior.CommandParameter="{Binding }"/>
I'd would recommend using a different event than KeyUp, since I don't think Images can have Keyboard focus so the KeyUp event will never get fired.
A better alternative is to use a Button and overwrite it's Template to be your Image. This will maintain the Click functionality, and give you access to Command and CommandParameter properties
<Button Command="{Binding DataContext.PrintCommand, ElementName=dataMyStuff}"
CommandParameter="{Binding }">
<Button.Template>
<Image ... />
</Button.Template>
</Button>
Also, the CommandParameter="{Binding }" will simply pass the current DataRow's DataContext (your data object) to the command
Change the data template to be a button that has a image as its content. Use the command and commandparameter properties on the button to call your printing method. You can declare your print command in your viewmodel, and bind to it. Your parameter could be the selected row in your datagrid.
I have the following xaml in my ui:
<ribbon:RibbonGallery SelectedValue="{Binding Text}"
SelectedValuePath="Content"
SelectedItem="{Binding SelectedRemark, Mode=TwoWay}"
MaxColumnCount="1">
<ribbon:RibbonGalleryCategory ItemsSource="{Binding Remarks}" DisplayMemberPath="Text"/>
</ribbon:RibbonGallery>
Both SelectedRemark and Remarks are properties on my view model; and Remarks is an ObservableCollection<Remark>.
It will display properly, and I can edit the text in the combobox. However, as soon as the combobox loses focus, it reverts back to whatever the the original text was.
I'm new to WPF, and cannot figure out what am I doing wrong.
Beware of a bug that causes the selectionchanged event to fire after the mouse moves. See this bug report: https://connect.microsoft.com/VisualStudio/feedback/details/666352/
Those bindings are all related to selection. I'm not certain how the Ribbon operates but it doesn't appear that what you are trying to do will give you the results you are after.
In addition the ObservableCollection<Remark> is only relative from an Add/Remove stance when making use of binding. It will not propagate changes to the items within the collection. If you were wanting that functionality you will need to implement INotifyPropertyChanged on the Remark object, then raise a property changed notification as needed.