I have a DataTemplate defined in XAML. I want to customize it and give it to DataGridTemplateColumn.CellTemplate. But when I call LoadContent(), the VisualTree is still null, instead a UIElement tree is returned. After I customize the tree, how can I convert it back to a DataTemplate? Or is there a way to feed the DataGrid cells directly with UIElement?
I think it should help you
Code Project
I've learned that once the UI controls are instantiated, it is impossible to convert back to a DataTemplate i.e. FrameworkElementFactory tree.
Related
I am trying to achieve something very similar to this:
WPF with Helix toolkit, animate with code-behind?
However, my scenarios is slightly different. I am trying to animate a tube (curve) defined by a path (TubePath) which undergoes deformation as a function of time (animation) defined by a mathematical function (calculated numerically).
My design/plan is to use a usercontrol (containing the Helix Tube control) to draw each frame of the tube defined by a path. I plan to make the TubePath property in my usercontrol which is an oservablecollection a dependency property. I plan to control the animation from my ViewModel (or View) by binding the CurrentPath property of the ViewModel to the usercobtrol TubePath property. I plan to drive my ViewModel from INotifyPropertyChanged. I will a have List of Paths (PathList) stored in advance of starting the animation in my Model. At each (so called) time or animation step, I will copy the corresponding path from the PathList to the CurrentPath in the VieModel. I am hoping that change in the the CurrentPath collection in the ViewModel will activate the binding which will force the user control to update the tube drawn by the usercontrol.
These are my questions:
(1) I have read that not all changes to an ObservableCollection fires propertychanged events. Will overwriting or refereshing the whole CurrentPath collection in the ViewModel update the TubePath in the UserControl which will force redrawing of the tune? Do I have to do anything special to achieve this kind of binding.
(2) I am new to WPF and animations with WPF. My research indicated that I could do the animation from my ViewModel in several ways: using the Dispatcher.Invoke() like in the example given above, or I could use the RenderingEventManager.AddListener() (and RenderingEventManager.RemoveListener() to stop animation) provided by the Helix Toolkit like it is done in example here:
https://github.com/helix-toolkit/helix-toolkit/tree/develop/Source/Examples/WPF/ExampleBrowser/Examples/Wind
or I could loop using DispatcherTimer() as done here:
Binding on DependencyProperty of custom User Control not updating on change
Any suggestions as to the best method as well as my concept of driving animation from the ViewModel would be greatly appreciated.
I have a main window coupled with a view model.This main window uses a usercontrol which also has its own viewmodel.
What I would like to achieve is setting a binding in the main window's xaml between one of its viewmodel's custom property and one of the usercontrol's viewmodel's custom property.
How would one go about doing that?
Could you instead use the ViewModels as projections of a Model?
That is, could you have a class that holds the state (or actions) that both the VMs need to expose and have both the VMs reference this class?
If for some reason you have to couple views to something outside their own DataContext I believe you can only go up the visual tree by using RelativeSource FindAncestor in the binding. I don't think you can traverse down (e.g. Window -> Control).
If you really want to Bind them together you could make your ViewModel's properties Dependency Properties and your ViewModel derive from DependencyObject - then you could do..
var binding = new Binding("Something");
binding.Source = myViewModel1;
binding.Mode = BindingMode.TwoWay;
BindingOperations.SetBinding(viewModel2,ViewModelType.SomethingProperty,binding);
If this is a good design having your viewmodels derive from DependencyObject is another question..
You could also try looking at this library that allows binding to and from POCOs.
I ended up not using a modelview for my usercontrol, not as neat but at least it works and is less complicated datacontext wise.
Thanks to all.
I have a WPF user control ...which is in MVVM. The user control(which contains a listview) need data from the page (where it is included). I have to set a property to get this data input. Will this comply with MVVM...if not, what is the way for the same?
I'm afraid this won't be correct in MVVM design pattern. try to stick to your view model to define properties. Why don't you consider moving that property to control's vm?
Use an ObservableCollection rather.
ObservableCollection<myModel> myOC = new ObservableCollection<myModel>();
where myModel is a class that has to be constructed transforming your columns in the DataTable to Properties.
In your MainViewModel, loop through the DataReader and create myOC out of it.
Now bind myOC to a ListView in your page.
The DataTemplate of ListView should be a view(UserControl) drawing data from a ViewModel constructed out of myModel
But your UserControl has the entire ListView inside. If that is on purpose, then let me know the entire design to give a better idea.
I'm trying to programmatically add events and elements to a DataTemplate in a Silverlight 3.0 app. I have a User Control with a dependency property where I would like to take the template that's set, tweak it, and then set the modified version to an inner control.
The idea I have is to take the DataTemplate that comes in, read its XAML, tweak it, and then use the XamlReader to create a modified DataTemplate that can then be set to the inner control. The issue with this approach is I don't know how to get the XAML from the originalal template (if it's even possible.) For example:
protected virtual void OnItemTemplateChanged(DependencyPropertyChangedEventArgs e)
{
// Get the original Xaml from the set template
//string originalXaml = ???
// Modify the template
string newXaml = originalXaml.Replace("foo", "bar"); // for example
// Create a new template from the modified XAML
DataTemplate newTemplate = (DataTemplate)XamlReader.Load(newXaml);
// Update the inner template
this._childDropdown.ItemTemplate = newTemplate;
}
Does someone know either: 1) if there's a way to read the original XAML, or 2) another approach to programmatically modify the DataTemplate.
Thanks,
You cannot manipulate the template via code (see documentation for FrameworkTemplate). The closest you are going to get is to call the DataTemplate's LoadContent to create an instance of the contained Xaml but you can't use that to manipulate the contents and there is no way inside Silverlight to convert a UIElement back to Xaml again.
The nearest I think you can get is to make your dependency object a Uri pointing to a Xaml resource that contains the initial DataTemplate.
You can then load this resource into an XDocument and manipulate it as XML. Subsequently you can use XamlReader to instance the DataTemplate and assign it to ItemTemplate.
I created a ListBox that has a DataTemplate as Itemtemplate. However, is there an easy way to access the generated UIElement instead of the SelectedItem in codebehind?
When I access SelectedItem, I just get the selected object from my
ItemsSource collection. Is there a way to access the UIElement (ie. the
element generated from the DataTemplate together with the bound object)?
You are looking for the ItemContainerGenerator property. Each ItemsSource has an ItemContainerGenerator instance. This class has the following method that might interest you: ContainerFromItem(object instance).
Once you have a handle to the ListBoxItem, you can go ahead and browse the logical and visual tree. Check out Logical Tree Helper and Visual Tree Helper.
Like Andy said in the comments, just because the item exists in your collection doesn't mean a container has been generated for it. Any kind of virtualizing panel scenario will raise this issue; UIElements will be reused across the different items. Be careful with that as well.
siz, Andy and Bodeaker are absolutely right.
Here is how I was able to retrieve the textbox of the listbox's selected item using its handle.
var container = listboxSaveList.ItemContainerGenerator.ContainerFromItem(listboxSaveList.SelectedItem) as FrameworkElement;
if (container != null)
{
ContentPresenter queueListBoxItemCP = VisualTreeWalker.FindVisualChild<ContentPresenter>(container);
if (queueListBoxItemCP == null)
return;
DataTemplate dataTemplate = queueListBoxItemCP.ContentTemplate;
TextBox tbxTitle = (TextBox)dataTemplate.FindName("tbxTitle", queueListBoxItemCP);
tbxTitle.Focus();
}
(Note: Here, VisualTreeWalker is my own wrapper over VisualTreeHelper with various useful functions exposed)