I'm currently migrating from WinForms over to WPF and I'm really struggling with the binding aspects. All i need to do is match the fill property of a rectangle to a textblock.background and keep them in sync. I know I can do this with 'classic' event handlers, but I have 24 textboxes and 24 rectangles, and I'd prefer a more WPF solution. I've toyed with the binding properties but I can't seem to get any type of results since I have no clue with type of binding I even need! Do i need an event, or use a convertor, or possibly a style trigger? Maybe just stick transparent tape on the screen and call it a day?
I know the following doesn't work but this is my level of understanding at this point.
<Rectangle Fill="{Binding Source="textBlock.Background"} />
I've read various articles on databinding but they are all much more advanced, and typically deal with data.
Can someone please shed some light on this helpless n00b!
<TextBlock x:Name="SomeTextBlock" Content="Hi"/>
<Rectangle Fill="{Binding ElementName=SomeTextBlock, Path=Background}"/>
That's the easy way if you are creating them in XAML.
Related
first of all I would like to thank you for the many good posts that i read in this forum. Unluckily I could not find anything of help for my current problem (either here or anywhere else).
What I'm trying to do sounds quite simple, but I have no clue how to get it to work ... perhaps I'm still to new to wpf or I don't thing wpfy enough :)
I'm designing a front end for a part in an automated manufacturing:
I have a quantity of places where pallets can be put (but it can be empty as well).
Each pallet has up to 3 places where parts can be mounted
Everything is created dynamically of a database and is reacting to changes.
The position of the parts on the pallet comes from the database as well and should be visualized
What I would like to have is:
An overview over the pallet-places with a preview of the pallet
When I select a place I want to see a detail view of the place
When I click on a part on the pallet of the detailed pallet I want to see details to the part
The first two points are quite simple and work nicely:
I have got a DataTemplate for every component (part, pallet, pallet-place). Actually those are UserControls that are imported as Datatemplates
the overview is a ListBox with the places as DataContext
for the detail-place-view I use the UserControl and bound it to the SelectedItem of the Listbox
I tried to bind the Text of a Textblock to the ID of the selected Part ... and fail.
Probably I could use some global variables in the code behind - but that sound very ugly.
Can anybody help?
I have got a solution ... it is not nice but works.
I created an event in the pallet, that triggers, when the selected part-place changes
I handle the event in the pallet-place and create a new one
And finally I handle it in the overview and change the detailview accordingly
Most likely there are much nicer solutions, but it will suffice.
Perhaps try an ElementName binding?
<TextBlock Text="{Binding ElementName=Name_of_your_Listbox, Path=SelectedItem.ID" />
Can you post a bit more code of your TextBlock and your Binding?
Context is important, if i use a ContentControl and bind its content to the SelectedItem like this:
<ContentControl Content="{Binding SelectedItem, ElementName=mylistbox}">
I can bind to the ID of the selected item in the DataTemplate like this:
<ContentControl.ContentTemplate>
<DataTemplate>
<TextBlock Text="{Binding ID}" />
</DataTemplate>
</ContentControl.ContentTemplate>
That is because setting the Content of the ContentControl automatically sets the DataContext as well, and this binding is relative to the DataContext since no source (ElementName, RelativeSource, Source) has been specified.
I do not know how your UserControl handles the context, if the DataContext is not affected such bindings will not work. You would need to bind directly then:
<uc:MyDetailsView Data="{Binding SelectedItem, ElementName=mylistbox}">
<!-- ... -->
<TextBlock Text="{Binding SelectedItem.ID, ElementName=mylistbox}" />
This of course defeats the purpose of having the binding on the UserControl itself in the first place. But unless you post some relevant code it's quite hard to tell what is wrong.
Also check the Output window in VisualStudio, binding errors will show up there and might provide valuable information as to what went wrong.
I want to change Button drawing based on button size using XAML.
I know it is possible using c# code not sure about XAML
Thanks
Update :
my code is like
<Grid Width="60" Height="60">
<Ellipse Width="57" Height="57" StrockThickness="1">
</Ellipse>
</Grid>
I am applying above style to Button control. but here Width/Height is hard coded. I want it dynamically design time. so when I increase/decrease button size ellipse become accordingly
Thanks again
You should be able to use Property or Event triggers (in XAML). This is probably the preferred way to do this kind of behaviour as it puts the User Experience completely in the designers hands (via XAML) rather than hooking up event handlers (in C# code) that a developer now needs to maintain in order to modify the user experience.
I don't have quick access to VS to test this out right now, but I can try tomorrow if there is no answer by then.
Does anybody have an idea how to change screens (views) in a MVVM View-First-Approach (The view instantiates the ViewModel:
DataContext="{Binding Source={StaticResource VMLocator},
Path=Find[EntranceViewModel]}"
)
For example:
In my MainWindow (Shell) I show a entrance view with a Button "GoToBeach".
<Window>
<DockPanel>
<TextBox DockPanel.Dock="Top" Text="{Binding Title}" />
<view.EntranceView DockPanel.Dock="Top" />
</DockPanel>
</Window>
When the button is clicked I want to get rid of the "EntranceView" and show the "BeachView".
I am really curious if somebody knows a way to keep the View-First Approach and change the screen (view) to the "BeachView".
I know there are several ways to implement it in a ViewModel-First Approach, but that is not the question.
Perhabs I missed something in my mvvm investigation and can't see the wood for the trees... otherwise i am
hoping for a inspiring discussion.
One possibility would be to have all views in the (MainWindow(Shell) and using Triggers for their visibility. But having a lot of different screens (views) all declared in the MainWindow doesnt feel right for me...
This question came up while reading this nice way of using MEF with MVVM I found on John Papas Blog: Simple ViewModel Locator for MVVM: The Patients Have Left the Asylum . But as nice as this marriage of view and viewmodel is, it seems like there is no way to change screens that satisfies me. :)
So in my opinion if you have a lot of screens(views) you better use a ViewModel-First-Approach...
This looks like it might help:
Creating a ViewModel : do it before or after model data is available?
Failing that, how about creating the ViewModel once only at startup, and assigning it to each View window as it's created (rather than creating a new ViewModel each time). Then just close the first View and open up a new View as required, reassigning the single ViewModel instance.
You may want to look at Prism (i.e. the composite application library). Prism facilitates navigation between views via the region manager. This might be overkill for your application and can take a while to get your head around. Prism also allows you to develop using the MVVM pattern as well.
You can find more information about prism and prism navigation in the Prism documentation.
I'm working on a set of controls that has a number of DependencyProperties. The properties are themselves DependencyObjects and created during the get method of the properties. During the Get method, they are also set back to the propertybag using the SetValue() method, so they are in fact valid in Xaml and their properties can be storyboarded without having to explicitly created in the the visual tree.
These DependencyObjects has all its properties as DependencyProperties as well, for supporting DataBinding. They are as mentioned above possible to use in Storyboards.
At the same time I'm developing special designtime support for Blend 3 for these properties and have created an InlineEditorTemplate in the form of a Control. I create the template and set it for the PropertyValueEditor like this:
var vectorEditControl = new FrameworkElementFactory(typeof (VectorEditorControl));
var dataTemplate = new DataTemplate {VisualTree = vectorEditControl};
InlineEditorTemplate = dataTemplate;
In the Control I have the following:
<Grid DataContext="{Binding Value}">
<StackPanel Orientation="Horizontal">
<TextBox Text="{Binding Path=X, Mode=TwoWay}"/>
<TextBox Text="{Binding Path=Y, Mode=TwoWay}"/>
<TextBox Text="{Binding Path=Z, Mode=TwoWay}"/>
</StackPanel>
</Grid>
The editor shows up and I can edit the data. And even while debugging, I see that it actually sets the data back to the DependencyProperties on the DependencyObjects, but nothing happens to the Xaml. So the data is actually not persisted in any way in the Xaml and lost when I close the Xaml file and open it again.
Is there anything I need to do specifically for it to actually get into the Xaml? I was under the impression that this would happen automatically?
Excellent Question!
The core issue you're running into a misunderstanding as to what PropertyEditors in Blend/Cider end up databinding to.
Consider this object graph:
- MyControl
-- MyControl.MyProperty
--- FooClass
---- FooClass.BarProperty
Let's look at a scenario where we have a PropertyEditor (of any type: Inline, Dialog or Extended) to property MyControl.MyProperty.
When inside MyPropertyPropertyEditor you'd expect to get a fully settable copy of FooClass and be able to manipulate it's members.
That's a good assumption, but the wrong one.
The core issue is that Blend/Cider have elaborate data structures that represent your model at design time. There's about 3-5 levels of abstraction in how Blend/Cider interact with an actual control.
Creating those levels of abstraction allows Expression Blend / Visual Studio designers to be leveraged between framewroks (Silverlight / WPF) and support advanced scenarios (like Property transactions and property chaining).
So, the value you actually get to DataBind to is just one of those levels of abstraction.
Don't believe me? In your custom PropertyEditor, register for this.DataContextChanged event and checkout the type in this.DataContext. You'll end up getting the PropertyValue class (or one of it's friends).
Every single property change you want persisted to XAML (and shown on the design surface) should go through those abstraction layers.
the question you have to ask yourself is "Where do I get one of these absteaction classes for my PropertyValue.Value property instance?".
Well, what I'd do if I were you is create a ModelItem around MyControl.MyProperty and set that as your PropertyEditor.DataContext.
We've shipped an example of using ModelFactory.CreateItem in the Silverlight Toolkit as part of the Chart DefaultInitializer: Source Code, Ning Zhang (Awesome Design Time Dev) explains about ModelItem
If you've got follow-up questions I'd consider pinging PeteBl or UnniR through the Silverlight Insiders mailing list.
Sincerely,
-- Justin
It partly solves my problem. I'm having a dialog with UnniR for a followup.
I couldn't see how I could use this together with the PropertyValueEditor, but for default values this is brilliant and something I'll implement ASAP.
Thanks.
I'm working on a Prism Composite application where I load different views into a region. I need to make sure that the view I'm loading is resized to the same height as the region. Each view is a usercontrol that has a Grid as the outer element. I'm using the following code
<Grid Height="{Binding RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type ItemsControl}}, Path=ActualHeight}">
To set the height of the grid. My problem is that this exact code works fine for one view and doesn't for another view. On the grid that doesn't work, the height is what I would expect as if the Height property is not being set.
Any suggestions on how to trouble shoot this.
Without knowing much, I'd say this issue really just boils down to a binding issue. Debugging bindings is tricky, but there is a really great article on the subject here:
http://www.beacosta.com/blog/?p=52
Use the "diagnostics:PresentationTraceSources.TraceLevel=High" approach that Bea describes and find out what element you are actually binding to by watching the output window. That ought to help figure out why it's failing.
Good luck.