I'm trying to databind a Run of a TextBlock in code at runtime, and I can't for the life of me figure out how.
Several sources on the internet suggest this isn't possible without some (not too pretty) additional workarounds, and, more importantly, it should completely fail when you try to do it in XAML.
Yet, in my application I have the following, which works beautifully:
<DataTemplate x:Key="PitchTemplate">
<Grid Width="120" Height="120" HorizontalAlignment="Center" VerticalAlignment="Center">
<TextBlock HorizontalAlignment="Center"
VerticalAlignment="Center"
TextAlignment="Center">
<Run Text="{Binding}" FontFamily="{StaticResource PhoneFontFamilySemiBold}" FontSize="36"/>
<LineBreak/>
<Run Text="{Binding Frequency, StringFormat=\{0:n2\}Hz}" FontFamily="{StaticResource PhoneFontFamilyNormal}" Foreground="{StaticResource PhoneSubtleBrush}"/>
</TextBlock>
</Grid>
</DataTemplate>
So I figured: If it can be done in XAML, it should be possible to do it in code.
Sofar, to no avail. Using the "regular" way of binding in code won't work; the Run class doesn't inherit from FrameworkElement, so doesn't have a SetBinding method, and it's Text property is not a DependencyProperty.
Using BindingOperations.SetBinding doesn't work because the Text property is not a DependencyProperty.
I'm up to the point that I'm willing to accept that it can't be done at runtime (although not without a last attempt at StackOverflow), but I'm still curious if
This can be done in code at runtime?
And if not:
How come it does work in XAML?
EDIT:
The example shown is just there to show that it can be done in XAML. The reason I need to create the bindings in code, is that I have a control that dynamically creates other elements, which need to be data bound.
UPDATE:
As Pete and I both found out, there is a dependency property for Text, but it's private. I assume that's why it does work through XAML (the xaml parser probably has more rights when it comes to reflection, and more knowledge in general about classes).
The upside is, that this means (tried & tested) it also works through XamlReader.Load(), which is (sofar) the cleanest solution I've come up with.
But if anyone has anything better, I'd be glad to hear about it.
Run.Text is backed by the private TextProperty which means you can't directly set its value without some reflection gimmicks, something like this:
Run r=new Run();
r.Text = "Moo";
var field=r.GetType().GetField("TextProperty", BindingFlags.Static | BindingFlags.NonPublic);
var dp=field.GetValue(null) as DependencyProperty;
BindingOperations.SetBinding(r, dp, new Binding {...});
This is rather ugly, but perhaps it can be useful.
You can find various workarounds for this. This SO post uses a custom attached property to configure binding. The attached property is used because Run is a sealed class in Silverlight so you can't create you own Run that supports binding.
The reason that it works in XAML but not in code-behind might be that there is a dependency property for Text, but it is private. It's a little bit 'black magic' to me though, so that's just a guess! This is a strange one, as in WPF the Run does inherit from FrameworkContentElement and has a SetBinding method...
Could you create a subclass of Run that contains a public DependencyProperty for text? I'm afraid I don't have the Silverlight dev tools to hand to try it out at the moment, but I'll try and take a look later.
Thanks both to Pete & Panagiotis for their efforts and suggestions (both 1 up).
In the end, I decided to go with my own solution (found in the "Update" section of the question): Create dedicated XAML strings containing the Run including the binding, and use XamlReader.Load() to parse it, and return a Run object.
The situation I'm working on is quite specific, so a local solution to the problem is good enough (for now). Reflection, as suggested by Panagiotis, won't work due to restrictions imposed by Silverlight. Lastly, the BindableRuns solutions would need either extensive work to deal with nested properties, or I would have to "uglify" my view model, so I discarded it (also for now).
Thanks all for your input.
Related
I made an application in WPF (.Net 4.7). For code protection, I am using .Net Reactor.
I am using following syntax to bind textblock to first element of list in my model.
<TextBlock Text="{Binding list[0].property1}"/>
This code works fine but after obfuscation, this code no longer works. I changed it to this
<WrapPanel DataContext="{Binding Path=list}">
<TextBlock Text="{Binding property1}"/>
</WrapPanel>
and this bind textblock to 'property1' of list first element (what I needed). I accidentally got this solution, I don't know if it is a proper way or not. I build application without obfuscation and above also works. Questions I have regarding this are
Why binding is not working like usual after obfuscation?
Using this method, does it always bind to first element of collection? If it always bind to first element, than I will continue deployment of application without wasting more time.
Sorry for bad English!!
I'm struggling to get a basic binding working without resorting to code behind.
I currently have:
<TextBlock Text="{Binding Goodbye, Converter={StaticResource MyConverter}, ConverterParameter={StaticResource SomeObject}}"></TextBlock>
Where I'm having to delve into codebehind to set the resource SomeObject:
this.Resources["SomeObject"] = this;
Is it possible to achieve the same effect in XAML-only?
I've tried using ...ConverterParameter={RelativeSource AncestorType={x:Type Window}}... which unfortunately passes in the expression rather than evaluating it which I guess makes sense.
Failing that, I think I'm going to scrap ConverterParameter and just use a MultiBinding, which feels like a bit of a hack.
Scenario: Developing a "thick" client in UWP, using c# destined for the desktop of Windows 8.1/10 (a store app).
In my user interface, I tried to use the following inline
<StackPanel Grid.Column="0">
<TextBlock x:Name="Qty_Size_Crust" Margin="25,10,20,0" Padding="0,0,0,0" TextAlignment="Left" TextWrapping="Wrap" MaxHeight="25" Foreground="#ff230909" FontFamily="Segoe UI" FontSize="16" xml:space="preserve" HorizontalAlignment="Left">
if ({Binding WidgetName} == "Backend")
{
<Run Text="{Binding ItemCode, Converter=ItemCodeToDescriptionConverter}"/>
}
else
{
<Run Text="See Administrator}"/>
}
</TextBlock>
The compiler would accept this, but during execution, I would neither see Item Description nor See Administrator. Is there something else I should be doing in order for this work? I was able to work around this by putting the code in the ViewModel, but wondered why this didn't work (or maybe it shouldn't).
XAML doesn't work with inline scripts so the answer is simply - it's not supported.
In your example - the condition code is simply added as text runs in the TextBlock, so the compiler accepts that.
As for the best solution to your specific problem - a condition in the view model is a good one. A TemplateSelector would work on the view side, but requires more code. View model might actually also be the best place to put it if you want to be able to test it, so it really is the right way to do it. Putting logic in the view layer would simply add code that can't be unit-tested.
Im building an application where I want to head for a design, that could remind of a dockpanel.
What I want, is having buttons in the left side (or left panel) representing different areas of the application (e.g "Milk", "Bread") and then have different "views" in the middle-panel.
What I already have tried, is making an application with a "Frontpage", and buttons changing the whole window/usercontrol - this however will not give me static areas/panels.
I do not want to use a tabcontrol with the tabtitemstrip being vertical - however it is kinda the same functionality im looking to have.
Any ideas?
Below is a picture with the wished design, to kinda give an idea of my thoughts.. Any help appreciated :)
http://s57.photobucket.com/user/RolleKn/media/wpfdesign_zps3737b014.jpg.html
If you use WPF, use ContainerControl or ContentPresenter for that.
In general, "switching Visibility On/Off" is not a good way to go. It forces the UI to create all objects, even those invisible ones, and to handle their data and events, etc.
And you need to switch it all manually.
WPF provides you with many mechanisms that can save you this. Some are smarter than others, some not.
One of the most basic mechanism in WPF is the Control and its Template property. You can replace whole your Grid+Contents+SwitchingVisibility idea with a single Control and switching its Template:
<Window.Resources>
<ControlTemplate x:Key="panel1"> ..carrots.. </ControlTemplate>
<ControlTemplate x:Key="panel2"> ..cucubers.. </ControlTemplate>
<ControlTemplate x:Key="panel3"> ..donkey.. </ControlTemplate>
...
</Window.Resources>
<Grid x:Name="LayoutRoot">
<Control x:Name="foo" />
</Grid>
Now, if you get the foo and set its .Template and set it to panel1, then the "carrots" will show up. if you set it to panel3, donkeys. And so on.
It's very powerful, but it will not be really handy due to some other things I won't cover. There are books and tutorials that explain Templates in depth. Also, this mechanism is really not designed for such task. It's the most basic one, and a good thing to know if you want to work in WPF, but there are more suitable ones here.
Second next powerful and still basic mechanism is ContentControl/ContentPresenter. They work almost in the same way (actually CC uses CP internally), so I'll skip it.
ContentControl is a smart control that knows how to automatically select a correct Template with respect to the data you are tryng to present.
So:
<Window.Resources>
<DataTemplate DataType="CarrotData"> ..carrots.. </..>
<DataTemplate DataType="CucumberData"> ..cucubers.. </..>
<DataTemplate DataType="DonkeyData"> ..donkey.. </..>
...
</Window.Resources>
<Grid x:Name="LayoutRoot">
<ContentControl x:Name="foo" Content="{Binding ..}" />
</Grid>
Note the change from 'ControlTemplate' to 'DataTemplate'.
Now, with this setting, you don't even need to switch templates manually. You just get the "foo" and set its Content to either:
a CarrotData object, that contains the carrot-related data
a CucumberData object, that contains the cucumber-related data
a DonkeyData object, that contains the donkey-related data
Once you set the data to be shown (i.e. foo.Content = carrots[5]), the ContentControl will pick the relevant template to be shown.
You can bind the Content property to just about anything. If you have some dataclass that contains carrots/donkeys and has a property CurrentThing, you can bind to it and ContentControll will switch the views automatically along with the changes to CurrentThing.
That's basics. There's much more to it, in almost any point I tried to briefly cover. For now, leave ControlTemplates. Read about DataTemplates and Bindings. Read about ContentPresenter (shows 1 template for 1 item) and ItemsControl (shows N items+templates). Then, read a little on MVVM pattern.
You will quickly see that "having everything in one Grid" and "switching Visibility" is an odd way to do it.
However, I wouldn't be fair if I didn't mention that everything has a cost included. Extensive use of templates and bindings makes your app a bit slower compared to what you could get when you do everything manually. But usually, doing it manually is just not really worth it.
Here's the problem: I have a data-bound list of items, basically a way for users to map a request to a response. The response is an xml-based file. I'm letting them queue these up, so I've used a combobox for responses. The responses will include the full path, so they get a bit long. I want the displayed text of the combobox to be right-justified so the user can see the file name. For my static controls, I just use ScrollToHorizontalOffset() when a file is loaded and I'm done. For this dynamic list, I'd like to do it in xaml.
The "somewhat ugly" solution would be to store all the ComboBox objects as they load... then I can call ScrollToHorizontalOffset() directly, but I'd really prefer to do it a cleaner way than that! EDIT: (Actually, this may not be reasonable. A quick look at trying to hack around this issue gets into some really awkward situations trying to map my datasource items to the controls)
I've tried HorizontalContentAlignment, that only impacts the "dropped-down" portion of the ComboBox.
I've also tried to hook other various loading events, but haven't found one that works.
Using an Item template you can decide what will be shown.
You can set tooltip. You can then also use converters to add the dots.
<ComboBox x:Name="ConfigurationComboBox" VerticalContentAlignment="Center" ToolTip="saved configuration" SelectionChanged="ConfigurationComboBox_SelectionChanged">
<ComboBox.ItemTemplate>
<DataTemplate >
<StackPanel>
<TextBlock Text="{Binding}" ToolTip="{Binding Path}"></TextBlock>
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
To measure the text, see Measuring text in WPF.