Is it possible to store some data in every item of a TreeView control? I mean, something useful (e.g. a string) besides the header text?
Thanks.
Yes, WPF is "lookless", so your actual data can be anything you want it to be, and a TreeView is just a Template used to display the data to the user in a pre-determined way.
You can overwrite any part of that Template to be whatever you want, and/or have it bind to your data however you want.
Edit
I'm no expert on using the TreeView, but if you had a DataContext of List<Folder>, and each Folder object had a Name and a FullPath property, your TreeView could look something like this:
<TreeView ItemsSource="{Binding MyFolderList}">
<TreeView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}"
ToolTip="{Binding FullPath}" />
</DataTemplate>
</TreeView.ItemTemplate>
</TreeView>
If you haven't already, I'd highly recommend looking into the MVVM design pattern when working with WPF. Basically your application is your classes (ViewModels), and the Controls/XAML (Views) are just a pretty layer that sits on top of your classes to make them user-friendly.
This is an important concept when switching from a WinForms TreeView to a WPF TreeView
It depends on what you mean by store data...
If you're just talking UI customization Rachel's answer above works.
If you're talking about storing arbitrary object values, such as information about the TreeViewItem, or maybe a relation between two items, you can use the Tag property of TreeViewItem. For example, I had to write a mapping UI where two trees linked together where each TreeViewItem from the first tree, could connect to 1 TreeViewItems of the second tree. I used the Tag property of the first TreeViewItem to store the connecting TreeViewItem.
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 have a collection of objects that I want to present. How can I do this? A listbox would do but each object has many attributes which I want to present. I already bound a listbox to a collection and I have all my objects listed. My question is regarding the visualization of the listbox and if the listbox is the correct thing to use or there is something else that I should use.
I find the existing answers to be a bit lacking, normally one would not process collections or boil their items down to a string, at the very best you would do some dynamic manipulation using a CollectionView (e.g. sorting, grouping), but normally you use Data Templating to display the individual items which allows you to use all their properties.
Further there are several controls which work well with collections, firstly you need to know if you want selection, if not an ItemsControl is a good choice, otherwise you should use a ListBox or ListView.
ListViews are normally employed if you have different views for your objects, e.g. a details view and a thumbnail view. You can use the ListView.View for this, there is one existing view in the framework, the GridView, which offers columns. What Matthew Ferreira suggested is exactly what you should not do with a ListView since you want to make the templates dependent on the current view, in fact that code does not even compile since DataTemplate can only have one child.
ListViews are supposed to encapsulate the view logic in their view so it can be changed at will. If you decide to use a ItemsControl or ListBox then setting the ItemTemplate is what you want to do. Read the Data Templating overview i linked to, it makes for a good starting point.
You might want to consider using a ListView control instead. ListView has support for columns if you are planning on showing several properties from your object. You can use the ItemTemplate property to format the display of your object. For example:
<ListView ItemsSource="{Binding Path=myObjectCollection}">
<ListView.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=Title}"/>
<CheckBox IsChecked="{Binding Path=ShouldCheck}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
This example assumes that your object has the properties Title and ShouldCheck.
Your collection of object is probably to be viewed as your model. The usual thing in WPF is to add a ViewModel that translates and exposes the model data into a form suitable for binding. Depending on what you want to do, your VM could e.g. format each object into a string representation and then expose it as a collection of strings that the Listbox can bind to and display.
In the above image, child is a ContentPresenter. Its Content is a ViewModel. However, its ContentTemplate is null.
In my XAML, I have a TabControl with the following structure:
<local:SuperTabControlEx DataContext="{Binding WorkSpaceListViewModel}"
x:Name="superTabControl1" CloseButtonVisibility="Visible" TabStyle="OneNote2007" ClipToBounds="False" ContentInnerBorderBrush="Red" FontSize="24" >
<local:SuperTabControlEx.ItemsSource>
<Binding Path="WorkSpaceViewModels" />
</local:SuperTabControlEx.ItemsSource>
<TabControl.Template>
<ControlTemplate
TargetType="TabControl">
<DockPanel>
<TabPanel
DockPanel.Dock="Top"
IsItemsHost="True" />
<Grid
DockPanel.Dock="Bottom"
x:Name="PART_ItemsHolder" />
</DockPanel>
<!-- no content presenter -->
</ControlTemplate>
</TabControl.Template>
<TabControl.Resources>
<DataTemplate DataType="{x:Type vm:WorkSpaceViewModel}">
....
WorkSpaceViewModels is an ObservableCollection of WorkSpaceViewModel. This code uses the code and technique from Keeping the WPF Tab Control from destroying its children.
The correct DataTemplate - shown above in the TabControl.Resource - appears to be rendering my ViewModel for two Tabs.
However, my basic question is, how is my view getting hooked up to my WorkSpaceViewModel, yet, the ContentTemplate on the ContentPresenter is null? My requirement is to access a visual component from the ViewModel because a setting for the view is becoming unbound from its property in the ViewModel upon certain user actions, and I need to rebind it.
The DataTemplate is "implicitly" defined. The ContentPresenter will first use it's ContentTemplate/Selector, if any is defined. If not, then it will search for a DataTemplate resource without an explicit x:Key and whose DataType matches the type of it's Content.
This is discussed here and here.
The View Model shouldn't really know about it's associated View. It sounds like there is something wrong with your Bindings, as in general you should not have to "rebind" them. Either way, an attached behavior would be a good way to accomplish that.
I think the full answer to this question entails DrWPF's full series ItemsControl: A to Z. However, I believe the gist lies in where the visual elements get stored when a DataTemplate is "inflated" to display the data item it has been linked to by the framework.
In the section Introduction to Control Templates of "ItemsControl: 'L' is for Lookless", DrWPF explains that "We’ve already learned that a DataTemplate is used to declare the visual representation of a data item that appears within an application’s logical tree. In ‘P’ is for Panel, we learned that an ItemsPanelTemplate is used to declare the items host used within an ItemsControl."
For my issue, I still have not successfully navigated the visual tree in order to get a reference to my splitter item. This is my best attempt so far:
// w1 is a Window
SuperTabControlEx stc = w1.FindName("superTabControl1") as SuperTabControlEx;
//SuperTabItem sti = (SuperTabItem)(stc.ItemContainerGenerator.ContainerFromItem(stc.Items.CurrentItem));
ContentPresenter myContentPresenter = FindVisualChild<ContentPresenter>(stc);
//ContentPresenter myContentPresenter = FindVisualChild<ContentPresenter>(sti);
DataTemplate myDataTemplate = myContentPresenter.ContentTemplate;
The above code is an attempt to implement the techniques shown on the msdn web site. However, when I apply it to my code, everything looks good, except myDataTemplate comes back null. As you can see, I attempted the same technique on SuperTabControlEx and SuperTabItem, derived from TabControl and TabItem, respectively. As described in my original post, and evident in the XAML snippet, the SuperTabControlEx also implements code from Keeping the WPF Tab Control from destroying its children.
At this point, perhaps more than anything else, I think this is an exercise in navigating the Visual Tree. I am going to modify the title of the question to reflect my new conceptions of the issue.
Hey guys,
I have a WPF TreeView that has three nodes, I would like the last child (the third node) to contain a ListView populated with my bound data. The issue that I'm running into is that if I put a ListView in the ItemTemplate of my HierarchicalDataTemplate I get a ListView for each child rather than a single ListView with content. This is expected behavior per the documentation, but I'm looking for a work around (possibly modify the ItemContainerStyle), unfortunately I have virtually no experience with the TreeViewItem's control template, or for that matter much experience with TreeViews in general.
I've looked at the posibility of using a TreeListView but it doesn't fit my use case, nor does binding a separate control and displaying data that way.
Has anyone either already gone through the headache of sandwiching a ListView into a TreeViewItem, or can someone suggest how to modify the ControlTemplate to accomplish this?
Thank you,
Aj
The node that has the Listview should be a different data type than the other two nodes so it can be handled differently by the Treeview.
Also it sounds like the child that contains the list view data should not be in a HierarchicalDataTemplate but a regular DataTemplate one, since it doesn't have other child elements recognized by the Treeview. You can mix and match HierarchicalDataTemplate and regular DataTemplates in a Treeview as you see fit, regular DataTemplates represent "leaf" nodes, they don't have any children.
sample with different data types used in Treeview but still using hierarchical templates:
<HierarchicalDataTemplate DataType="{x:Type FooNormal}" ItemsSource="{Binding TreeviewChildNodeCollection}">
// do something else here.
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="{x:Type FooList}" ItemsSource="{Binding TreeviewChildNodeCollection}">
<ListView ItemsSource="{Binding ListviewChildNodeCollection}">
//use listview here
</ListView>
</HierarchicalDataTemplate>
Turns out the easiest way to deal with the situation is to replace the HierarchicalDataTemplate on the second node with an Expander, set the ItemsSource on the ListView rather than the HierarchicalDataTemplate, and restyle the button on the Expander to look like the one from a TreeViewItem....sorta a hack but it works :)
Thanks for all the help,
Aj
I'm brand spanking new to WPF and am trying to play around with projects to better understand what I'm reading.
My understanding of a resource is that it is the instance, you can't use it like a factory and create instances of it. For example, a XAML-defined rectangle. You can reference it, but you can't have numerous instances of it all over the surface.
In WPF, what would be the way to do that? If I define a Rectangle as a resource with specific properties and wanted to have multiple instances of that within a dynamically-generated grid, how should I be going about it? Or is there a different way I should be trying to do this?
Purely academic exercise with no real-world application.
Actually there's nothing about resources in particular that prevents you from using it multiple times. A perfect example of this is brush resources, style resources, etc. You define them in XAML and the XAML parser creates a single instance of the resources and stores them in the resource dictionary and these brushes, styles, etc can be used as property values many times even though only a single instance of the resource was created.
But having said that, as you noted, you can't really define a Rectangle resource and use it multiple times in the visual tree. This has nothing to do with the fact that it's a resource, but rather it has to do with the fact that a FrameworkElement cannot be a child of more than one parent element.
So what we have instead is called "templates". These tell WPF how to create an element tree but does not actually create the tree until you instantiate the template. Below is an example.
<UserControl>
<ItemsControl ItemsSource="{Binding WholeBunchOfItems}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid>
<Rectangle Fill="Yellow" />
<ContentPresenter Content="{Binding}" />
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</UserControl>
In this example I've bound an ItemsControl to a collection of some sort. For each item in the collection, the ItemsControl will use my DataTemplate to render the item. Within a DataTemplate you can use data binding to access the current item.
I would suggest reading up on MSDN about ControlTemplate, DataTemplate, and Style. These are all important concepts in WPF/Silverlight.
To get multiple instances replicated across a grid or listbox, you need to set the data template to define the UI controls for each row of data, and then databind the grid or listbox to a collection of data that determines how many rows and the individual field values.
Key term for you to research first: data template.