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I usually find this is an issue for two reasons:
- A (dependency) property on a control is not being set in the default or specified style. This usually happens most on custom controls or controls where I have overridden the default template. Specifying a default value for a property in the default style will usually make this one go away.
- A custom control (or extended control) doesn't handle the binding to a null object correctly. If, for example, you have something bound to a property on a view model but that property is a nullable type, in design mode it will probably be null. When the design surface mocks the VM to present a design-time view, the property evals to null and can throw an exception if the control doesn't handle it properly. If it is a control you wrote/overrode, you can fix it by handling a null value bound to the offending DP. Otherwise, add design-time code to provide a valid value for the offending VM property. (If you are using a framework like MVVMLight, IsInDesignMode is part of the VM base class. Otherwise, System.ComponentModel.DesignerProperties.GetIsInDesignMode will tell you.
Beyond this, good luck. Xaml designer exceptions are especially painful to try to decode. It won't make you feel any better but I've even had the design surface crash repeatedly but clear up after a reboot.
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Yeah. If I do a Clean and then a Rebuild, it displays nicely...for a few minutes, then goes back to not being able to display the controls.
It's just annoying. Of course, any changes I make to the user controls are done on themselves, not on their parent, so it's not a problem as such. Just grrrr. :p
I just can't figure what I could possibly have done to make it stop working after it has been working for so long.
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It usually gives you a pretty damn good hint as to what's wrong. Either in the error dialog or red / blue squiggles. It's entirely possible to have your XAML squiggled without seeing the error dialog. Some people like to ignore those squiggles, but 11 times out of 10, they indicate a real problem.
If you aren't getting an error dialog or squiggles, you can add a global exception handler to your app and pop up a message box, do a full re-build and restart Visual Studio. When it loads your XAML and gets the exception, it'll pop up the message box.
You are probably accessing something that isn't available / initialized yet at design time.
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Yep.
No squiggles, though. And the Stack Traces and Inner Exceptions pointed to all sorts of bizarre places having nothing to do with the actual problem:
App.Current.Windows[0]
App is apparently not available at designtime.
So I wrapped the place it was being used in
<a href="http://www.youtube.com/GenJerDan">YouTube</a>
and
My <a href="http://www.persongo.net/">Mu[sic], Films and Windows Programs, etc.</a>
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I am creating an app that will replace the Linq-To-SQL designer. Most of the code you see is from other apps I found on CP or other places all pieced together.
My app is here[^]. So far there's not much there.
If you run it you will see a mock table on the designer surface. It can be moved around. There is Select checkbox in the upper left corner of the main window. Checking it turns on the table's adorners for sizing.
Problem:
What I want to do is turn on the sizing adorners on the table when the table's header or footer area is clicked. But because both the header & footer border controls have their IsHitTestVisible set to False, the MouseDown even doesn't fire.
I'm not really sure how to make this work. I could use some help.
Many thanks!
If it's not broken, fix it until it is
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I'm not sure the hit test is the problem. I didn't dive in really deep but when you move your mouse over the table, the cursor switches to the cross to indicate moving the table. However, you have to click to move the table. I'm guessing that clicking on the header of the table is actually activating the table move logic... meaning the "move" action is swallowing the click on the header you want.
I suggest moving that table move functionality down. If you want to click on the header and show the size adorners then move the cross/table move functionality down in the visual tree. Or switch to a double-click to show the size adorners. (That would seem more "normal" to me anyway)
HTH!
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I understand that when you drag a table onto the designer surface the designer will add relation lines to other tables in the designer if there are corresponding FK's.
If you remove a relation will the underlying DB will still enforce FK violations?
If so, so what purpose do the relations serve in the designer?
Thanks
If it's not broken, fix it until it is
modified 10-Feb-14 13:38pm.
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I have a boolean value to which radio buttons are bound, like so:
<RadioButton x:Name="Aye"
GroupName="wah"
IsChecked="{Binding IsChecked}">
<TextBlock>Yes</TextBlock>
</RadioButton>
<RadioButton x:Name="Nae"
GroupName="wah"
IsChecked="{Binding IsChecked,
Converter={StaticResource boolInv}}">
<TextBlock>No</TextBlock>
</RadioButton>
In VM property looks like this:
private bool isChecked;
public bool IsChecked
{
get { return isChecked; }
set
{
if (isChecked!= value)
{
isChecked = value;
OnPropertyChanged("IsChecked");
}
}
}
If the bound value is true, when I first open the screen the Yes checkbox is checked. I can select yes or no and they will display and save correctly. However, if I open the screen with a no value, nothing is checked. I believe the problem lies in the fact that when IsChecked is false, the converter converts that value to true in order to display the No box as checked, but in doing so it sets the IsChecked property to true, which then means that the No button should not be checked. The converter is the standard bool inverter all over the internet.
I didnae write this code, just trying to debug it.
Cheers, --EA
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Have you tried setting Mode=OneWay on the "Nae" binding?
<RadioButton x:Name="Nae"
GroupName="wah"
IsChecked="{Binding IsChecked, Converter={StaticResource boolInv}, Mode=OneWay}">
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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have a Listbox in which I have added two controls i.e a Checkbox and a Datagrid side by side as a Listboxitem. I have done it in a following manner:
In Code behind: listBox1.items.Add(dt)
here dt is the table name.
In Xaml:
<ListBox Grid.Row="0" AlternationCount="2" MinHeight="305" HorizontalAlignment="Stretch" Name="listBox1" VerticalAlignment="Stretch" MinWidth="537" >
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Name="stkPanel" MinHeight="80" MinWidth="500" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="40"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<DataGrid Grid.Column="1"
AutoGenerateColumns="True"
MinHeight="75"
HorizontalAlignment="Center"
Name="dataGrid1"
VerticalAlignment="Stretch"
MinWidth="470"
MaxWidth="900"
ItemsSource="{Binding}"
IsReadOnly="True" Background="#E6BAB7B7">
<DataGrid.ColumnHeaderStyle>
<Style TargetType="DataGridColumnHeader">
<Setter Property="ContentTemplate">
<Setter.Value>
<DataTemplate>
<CheckBox Name="colCheckBox" IsChecked="{Binding IsChecked, ElementName=IsDone, Mode=OneWay}" Content="{Binding}"/>
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
</DataGrid.ColumnHeaderStyle>
</DataGrid>
<CheckBox Grid.Column="0" Height="35" Width="25" Name="IsDone" HorizontalAlignment="Right" VerticalAlignment="Center" Checked="IsDone_Checked" />
</Grid>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Suppose for first listboxitem, there is "IsDone" checkbox and a datagrid. If I select "IsDone" check box (listbox item) all the datagrid column header check box is selected.Now, I can uncheck some of the datagrid coulmn header check boxes.What I want is to get values of the entire column only whose columnheader check box is checked and bind those values to a datatable.Similarly repeat the above process for other listbox item.Can you please suggest me how to do that in wpf?
modified 6-Feb-14 0:39am.
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I'm creating an HwndHost subclass in C++/CLI to render DirectX contents.
I got it working but...
When I debug and select win32 and native check I often get this exception when I exit my sample app:
First-chance exception at 0x75212EEC (KernelBase.dll) in WRLDesktop.exe: 0x0000071A: The remote procedure call was canceled, or if a call time-out was specified, the call timed out.
If there is a handler for this exception, the program may be safely continued.
When I look at the (external) call stack I get that:
wtsapi32.dll!56eb210f() Unknown
WindowsBase.ni.dll!5cf134c8() Unknown
[Managed to Native Transition]
PresentationCore.dll!System.Windows.Interop.HwndTarget.Dispose() Unknown
PresentationCore.dll!System.Windows.Interop.HwndSource.Dispose(bool disposing) Unknown
PresentationCore.dll!System.Windows.Interop.HwndSource.OnHwndDisposed(object sender, System.EventArgs args) Unknown
WindowsBase.dll!MS.Win32.HwndWrapper.Dispose(bool disposing, bool isHwndBeingDestroyed) Unknown
WindowsBase.dll!MS.Win32.HwndWrapper.WndProc(System.IntPtr hwnd, int msg, System.IntPtr wParam, System.IntPtr lParam, ref bool handled) Unknown
WindowsBase.dll!MS.Win32.HwndSubclass.DispatcherCallbackOperation(object o) Unknown
WindowsBase.dll!System.Windows.Threading.ExceptionWrapper.InternalRealCall(System.Delegate callback, object args, int numArgs) Unknown
WindowsBase.dll!MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(object source, System.Delegate method, object args, int numArgs, System.Delegate catchHandler) Unknown
WindowsBase.dll!System.Windows.Threading.Dispatcher.LegacyInvokeImpl(System.Windows.Threading.DispatcherPriority priority, System.TimeSpan timeout, System.Delegate method, object args, int numArgs) Unknown
WindowsBase.dll!MS.Win32.HwndSubclass.SubclassWndProc(System.IntPtr hwnd, int msg, System.IntPtr wParam, System.IntPtr lParam) Unknown
[Native to Managed Transition]
user32.dll!74cf7694() Unknown
user32.dll!74cf95ab() Unknown
So, it seems there is an HwndTarget that is deleted when it shouldn't, or deleted twice, I dunno...
What could be wrong?
My implementation is like the few sample on the web, along those lines:
public ref class D2DHost : public HwndHost
{
private:
HWND mWnd;
public:
D2DHost() {}
protected:
virtual HandleRef BuildWindowCore(HandleRef hwndParent) override
{
HWND parentHwnd = (HWND)hwndParent.Handle.ToPointer();
mWnd = ::CreateWindowEx(0, "static", NULL,
WS_CHILD | WS_VISIBLE,
0, 0, 100, 100,
parentHwnd,
NULL,
(HINSTANCE)GetModuleHandle(NULL),
NULL);
if (!mWnd)
return HandleRef(nullptr, System::IntPtr::Zero);
return HandleRef(this, IntPtr(mWnd));
}
virtual void DestroyWindowCore(HandleRef hwnd) override
{
::DestroyWindow(mWnd);
}
};
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I have written a general XML editor using a tree view with the help of code found around the net, but I want to fire an event after editing an attribute so that I can save the tree for Undo/Redo functionality, I have added 2 event handlers for NodeChanged and NodeInserted which fire when I load the XML file, but if I edit the attribute in the treeview in the textblock, the NodeChanged Event does not fire. Please could someone help me fire something off at this point so I can save info for UNDO purposes, I would prefer to only fire the event on the TextBox Losing focus ideally.
I am using a HierarchicalDataTemplate with a XmlDataProvider and MVVM
XAML
<Window.Resources>
<HierarchicalDataTemplate x:Key="NodeTemplate">
<StackPanel Orientation="Horizontal">
<TextBlock x:Name="name" Text="" FontSize="14"/>
<TextBlock x:Name="inter" Text=" " />
<TextBox x:Name="value" Text="" FontSize="14" />
</StackPanel>
<HierarchicalDataTemplate.ItemsSource>
<Binding XPath="child::node()|attribute::*" />
</HierarchicalDataTemplate.ItemsSource>
<HierarchicalDataTemplate.Triggers>
<DataTrigger Binding="{Binding Path=NodeType}" Value="Element">
<Setter TargetName="name" Property="Text" Value="{Binding Path=Name}"></Setter>
</DataTrigger>
<DataTrigger Binding="{Binding Path=NodeType}" Value="Text">
<Setter TargetName="value" Property="Text" Value="{Binding Path=Value}"></Setter>
</DataTrigger>
<DataTrigger Binding="{Binding Path=NodeType}" Value="Attribute">
<Setter TargetName="name" Property="Text" Value="{Binding Path=Name}"></Setter>
<Setter TargetName="inter" Property="Text" Value=": "></Setter>
<Setter TargetName="value" Property="Text" Value="{Binding Path=Value}"></Setter>
</DataTrigger>
<DataTrigger Binding="{Binding Path=NodeType}" Value="CDATA">
<Setter TargetName="value" Property="Text" Value="{Binding Path=Value}"></Setter>
</DataTrigger>
<DataTrigger Binding="{Binding Path=NodeType}" Value="Comment">
<Setter TargetName="value" Property="Text" Value="{Binding Path=Value}"></Setter>
</DataTrigger>
<DataTrigger Binding="{Binding Path=NodeType}" Value="ProcessingInstruction">
<Setter TargetName="value" Property="Text" Value="{Binding Path=Value}"></Setter>
</DataTrigger>
</HierarchicalDataTemplate.Triggers>
</HierarchicalDataTemplate>
<XmlDataProvider x:Key="xmlDataProvider"></XmlDataProvider>
</Window.Resources>
<Grid>
<TreeView Margin="0,24,0,273"
Name="treeView1"
Background="AliceBlue"
ItemsSource="{Binding Source={StaticResource xmlDataProvider}, XPath=*}"
ItemTemplate= "{StaticResource NodeTemplate}"
TreeViewItem.Selected="TreeViewItemSelected"
SelectedItemChanged="SelectedItemChanged">
</TreeView>
</Grid>
ViewModel
public XMLDataViewerModel(bool largeRegisters, XmlDataProvider dataProvider)
{
DataProvider = dataProvider;
DataProvider.Document = new XmlDocument();
DataProvider.Document.NodeChanged += new XmlNodeChangedEventHandler(Document_NodeChanged);
DataProvider.Document.NodeInserted += new XmlNodeChangedEventHandler(Document_NodeChanged);
Undo = new Deque<XmlDocument>();
Redo = new Deque<XmlDocument>();
// XDoc = DataProvider.Document;
}
void Document_NodeChanged(object sender, XmlNodeChangedEventArgs e)
{
// SaveForUndo();
}
void Document_NodeInserted(object sender, XmlNodeChangedEventArgs e)
{
// SaveForUndo();
}
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I have also now tried using interactivity on the TextBox on the FocusLost, but get the following error. I have a command LostFocusCommand in my ViewModel, but it expects to see it on Object "XmlAttribute". How Can I do this as this is somewhere within the Document of the XmlDataProvider I assume?
<TextBox x:Name="value" Text="" FontSize="14" >
<i:Interaction.Triggers>
<i:EventTrigger EventName="LostFocus">
<i:InvokeCommandAction Command="{Binding LostFocusCommand, Mode=OneWay}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</TextBox>
System.Windows.Data Error: 40 : BindingExpression path error: 'LostFocusCommand' property not found on 'object' ''XmlAttribute' (HashCode=38729837)'. BindingExpression:Path=LostFocusCommand; DataItem='XmlAttribute' (HashCode=38729837); target element is 'InvokeCommandAction' (HashCode=20475002); target property is 'Command' (type 'ICommand')
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Let's say I want to subscribe to the Page.Loaded or Page.Initialized event, but I don't want the event handler in my code-behind implementation of the derived Page class, I want it wired up to either a static handler in some other class or a handler in an instance of another class.
How do I do that? I've been searching and searching, and no luck.
Marc
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What you need to do is wire up an EventToCommand to a command in the ViewModel.
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Pete O'Hanlon wrote: What you need to do is wire up an EventToCommand to a command in the ViewModel.
Thanks Pete. I looked up EventToCommand -- so, if I understand this correctly, it's not part of WPF but something that someone else wrote? And if I understand this also correctly, I can't just tell the WPF parser/BAML "here's some instances of things you should know about because I want to wire up events to handlers in those instances?" Or, even if I instantiate those other things, I can't bind events to handlers in those other instances?
Ummm...If all that is true, I would have to say, I'm really disappointed with XAML.
Marc
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Marc Clifton wrote: if I understand this correctly, it's not part of WPF but something that someone else wrote?
Correct.Marc Clifton wrote: f I understand this also correctly, I can't just tell the WPF parser/BAML "here's some instances of things you should know about because I want to wire up events to handlers in those instances?" Or, even if I instantiate those other things, I can't bind events to handlers in those other instances?
Again, correct - well correct(ish). As I don't really know what you're trying to accomplish here, I can't offer any concrete advice other than to say that your page may be made up of multiple user controls - each with their own DataContext, and the events would be coming via that route. Of course, the way I would tend to handle something like what I think you are trying to accomplish would be to inject the class that you have that's currently static as a dependency and expose it as a property that way. Now my view can bind directly to it - it's clean and easy to test.
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What Pete says - but out of interest, why not put it in the code behind?
MVVM # - I did it My Way
___________________________________________
Man, you're a god. - walterhevedeich 26/05/2011
.\\axxx
(That's an 'M')
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You know precisely why not, your'e just stirring the pot. "the purist" approach it to have no code behind.
Never underestimate the power of human stupidity
RAH
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No I don't, no I"m not.
What is this 'purist' approach of which you speak?
My understanding of the pattern is that the GUI stuff is separated from the ViewModel stuff. MVVM != WPF and in WPF both CAML and .cs code behind are used together to build a class. It is that class's responsibility to provide the UI to implement the ViewModel, as it were.
Nowhere in the MVVM pattern does it prescribe anything to do with code behind.
So some folk have taken it upon themselves to say 'thou shalt not have code behind' because (I think) if they don't , some careless programmers will start putting business logic in the code behind - which is bad, not because it is in the code behind but because it is in the UI class which should not be implementing business logic.
But I don't understand why people feel the need to write additional Xaml functionality - often quite complex and usually a variation on some theme functionality - to avoid using two or three lines of code in the code behind.
I believe it is wrong, as having UI functionality in C# in code behind is often more 'obvious' to the maintenance programmer, and frequently less complex.
MVVM # - I did it My Way
___________________________________________
Man, you're a god. - walterhevedeich 26/05/2011
.\\axxx
(That's an 'M')
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_Maxxx_ wrote: but out of interest, why not put it in the code behind?
1. It seems ridiculous to put the event wire-up in the code-behind when in my opinion, I would think XAML should be able to handle the wire-up declaratively.
2. I don't want the functionality in the Page's code-behind because I have functionality that is common to all pages but needs to be wired up to each button on the page.
3. It's ridiculous to me to write a code-behind handler in each page for each button that then calls some common code elsewhere -- why can't I just wire up the event in the XAML?
4. Clearly I can wire-up the event in the code-behind, why would I be restricted from doing exactly the same thing declaratively in the XAML?
So far, doing this one simple thing, it appears I have stumbled across a serious XAML inadequacy. Is that correct?
(And please, don't go on about MVVM and all that rot -- there are many scenarios where MVVM is not the right approach, and I happen to be dealing with one of them.)
Marc
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Marc Clifton wrote: 1. It seems ridiculous to put the event wire-up in the code-behind when in my opinion, I would think XAML should be able to handle the wire-up declaratively.
I agree - it should, but it doesn't in many cases. So many folk write their own event-to-command handlers and the like to add that functionality. I personally don't like the approach of having heavy framework code to support something that should be simple out-of-the-box.
Marc Clifton wrote: 2. I don't want the functionality in the Page's code-behind because I have functionality that is common to all pages but needs to be wired up to each button on the page.
Buttons are different - buttons support commands so you can bind a button to a command, no problems, in your Xaml
Marc Clifton wrote: 3. It's ridiculous to me to write a code-behind handler in each page for each button that then calls some common code elsewhere -- why can't I just wire up the event in the XAML?
As mentioned, for Buttons you can, but not for all events. So 9for example) a double-click on some gui element will need 'something' in addition to out-of-the-box xaml.
Marc Clifton wrote: 4. Clearly I can wire-up the event in the code-behind, why would I be restricted from doing exactly the same thing declaratively in the XAML?
Because the developers in MS didn't implement the functionality - I don't know of any underlying problem that would stop you being able to do this - after all, there are lots of 'tricks' ot there to effectively give you this functionality.
Marc Clifton wrote: So far, doing this one simple thing, it appears I have stumbled across a serious XAML inadequacy. Is that correct?
IMHO yes.
Marc Clifton wrote: (And please, don't go on about MVVM and all that rot -- there are many scenarios where MVVM is not the right approach, and I happen to be dealing with one of them.)
I wouldn't dream of it  Regardless as to whether you are using MVVM or spaghetti-hoop code, it would seem remarkably sensible for XAML to support event-to-DataContextMethod out of the box.
Incidentally (& I'm thinking out loud) you could have a base View class possibly, with the event handler in there which your many XAML views could use? (i'd have a play myself, but I'm not in front of my Windows dev environment right now.
MVVM # - I did it My Way
___________________________________________
Man, you're a god. - walterhevedeich 26/05/2011
.\\axxx
(That's an 'M')
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I've been reading that this can't be done.
Here's an example:
<Page.CommandBindings>
<local:StateCommandBinding
Command="{x:Static local:Pages.ChooseLanguage.CustomRoutedCommand}"
Executed="{x:Static local:Commands.ExecutedCommandEnglish}"
CanExecute="CanExecute"
State="SwipeCardToBegin" />
</Page.CommandBindings>
Where StateCommandBinding is derived from CommandBinding. This works fine if ExecutedCommandEnglish is defined in the Page, but here I'm trying to wire it up in its own "controller" class, if you will, a static class with a static public method.
Ideas?
Marc
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I have a dataset and I want to bind my richtextbox to a field so that it autopopulates and when user leaves the textbox it validates for changes and updates the database field. How do I do this in WPF?
In winforms it is simple as rtb.Databindings.Add("Text", datasource, datafield)
but this is not in WPF
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You have posted this in the C# forum - and you were pointed in the right direction. No one is going to do the work for you. Go through the answers in the link you were given and test some of them out. And don't cross post questions.
When I was a coder, we worked on algorithms. Today, we memorize APIs for countless libraries — those libraries have the algorithms - Eric Allman
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