There seems to be many variations of this question, but none that deal with my scenario.
I have a UserControl that is used in several places. The control has a context menu, but some of its parents also have context menus. The parent context menus are not databound, i.e. they look like this:
<ContextMenu>
<MenuItem Header="Do Something" Click="DoSomethingMenuItem_Click" />
</ContextMenu>
I can walk up the logical tree and find the parent context menu, but I can't find a way to duplicate the MenuItems (I have to duplicate them because they are only allowed one parent).
I think I am asking a very similar question to this one: https://stackoverflow.com/questions/4177298/how-to-merge-wpf-contextmenus But it has not been answers so I'm still searching!
Please don't suggest I data bind the parent control and use composite collections - there are too many places this is used to make that feasable!
Honestly WPF has no direct way to merge context menus (rather menuitems) from the visual / logical tree of controls.
One way yu can acheive it is instead of setting the direct context menu property of your control, implement an attached property say MergedContextMenu which will be of type context menu.
Now in the property changed event...
Create a temporary context menu say currentContextMenu.
Clone the menuitems from the current value i.e. (e.NewValue as ContexteMenu).Items. Add these cloned menuitems into the currentContextMenu.
Traverse the logical tree and perform step 2 for each context menu found until your desired ancestor is reached.
Assign this currentContextMenu to the actual ContextMenu property i.e. ((UIElement)depObj).ContexteMenu = currentContextMenu.
Use the following code for Clone method....
public static UIElement cloneElement(UIElement orig){
if (orig == null)
return (null);
string s = XamlWriter.Save(orig);
StringReader stringReader = new StringReader(s);
XmlReader xmlReader = XmlTextReader.Create(stringReader, new XmlReaderSettings());
return (UIElement)XamlReader.Load(xmlReader);
}
Add the MenuItems from each original ContextMenu to a temporary list object, remove them from the original ContextMenus Items collection, and then add them all to the new ContextMenu. So long as the MenuItems are not contained on more than one ContextMenu at once you will be fine.
Related
On button click, Updating the ListBox ItemsSource collection.
For 4 or 5 clicks its working fine but afterwards it throws an exception as '[Unknown]' property does not point to a DependencyObject in path '(0).(1)[1].(2)'
I googled it & find the reason for it.
"The ElementControl overrides PrepareContainerForItemOverride and
calls PrepareModel to insert a mesh into _modelContainer for each
Item. Later in ElementFlow.BuildTargetPropertyPath (which is called
via ElementFlow.SelectItemCore -> LayoutBase.SelectElement ->
ElementFlow.PrepareTemplateStoryboard) it is assumed that such a mesh
has been inserted into _modelContainer. This exception occurs when the
mesh has not been inserted into _modelContainer. WPF calls
PrepareContainerForItemOverride on ApplyTemplate. This is only done
once. Items added later are never processed like that. "
So please provide me a solution to overcome it.
It seems like maybe there is an item in your " itemsource collection" that is not of the right type, or does not contain one of the properties that your listbox itemstemplate is looking for. Or, perhaps if you have different classes in your collection, one of them may not have the property you are looking for as a DependencyProperty. If it is just a plain property, it may not work correctly.
Check all object types that are going into your itemssource collection and make sure they all have DependencyProperties that are named what the itemstemplate is looking for.
How can an AttachedProperty which is a single property defined by an owning parent element, be set with multiple values through several child elements of that parent?
For example:
If I have:
<DockPanel>
<CheckBox DockPanel.Dock="Top">Hello</CheckBox>
<CheckBox DockPanel.Dock="Bottom">World</CheckBox>
</DockPanel>
Here we have a single DockPanel element and it has a single Dock property. How can it be set to "Top" and then "Bottom" simultaneously?
It will end up in a method looking like this
public class DockPanel : Panel
{
public static readonly DependencyProperty DockProperty;
// ...
public static void SetDock(UIElement element, Dock dock)
{
element.SetValue(DockProperty, value);
}
}
As you can see, it's actually not set on the parent, but the CheckBox itself, through the static method SetDock on DockPanel and not the parent instance. Doing it in code behind makes this a little clearer, notice how we never use an instance of a DockPanel.
DockPanel.SetDock(checkBox1, Dock.Top);
DockPanel.SetDock(checkBox2, Dock.Bottom);
Hopefully this was clear, unless your question was how this works "under the hood". In that case, see this question.
Quote from link.
The purpose for this mechanism is to
"attach" to other objects information
needed by parent objects, not the
child objects themselves.
A CheckBox has no use for a Dock property unless it is in a DockPanel. Same goes for Grid.Row, Canvas.Left, Validation.HasError (read only) etc. So basically, the DockPanel is the one needing the information, but it needs all its childs to be able to store it. Hence, it's using an Attached Property for it. If you created a new Panel, called PuneetPanel, and you needed an Angel to calculate the child position, then you could define your own Attached Property, PuneetPanel.Angel inside this panel and all childs could use this without having to be subclassed.
This is a very nice question. The answer lies in how the AttchedProperty works. The AttachedProperty is used by the parent to render a child. Before rendering the child, the parent looks out for any attached property defined on child and applies to the child.
I found this from msdn which might be useful for you ::
DockPanel defines the DockPanel.Dock attached property, and DockPanel has class-level code as part of its rendering logic (specifically, MeasureOverride and ArrangeOverride). A DockPanel instance will always check to see whether any of its immediate child elements have set a value for DockPanel.Dock. If so, those values become input for the rendering logic applied to that particular child element....
You can see this link to get detailed overview ::
http://http://msdn.microsoft.com/en-us/library/ms749011.aspx
Hope it helps you!!
For your own custom attached properties there are two options to achieve what you are looking for:
1. If the number of combinations of settable values are not to complex you could make your attached property of type enum that has the FlagsAttribute set. You can the combines the values you want to set using bitwise-or |:
[Flags]
public enum MultiDock
{
Left,
Top,
Right,
Bottom
}
And its usage in code:
MyCustomPanelOrWhatever.SetMultiDock(MultiDock.Left | MultiDock.Bottom);
This has one small proplem though, you can not do the above in xaml directly, you would have to write a MarkupExtension that can convert string to flagged enum values. Its usage would then look like this:
<CheckBox src:MyCustomPanelOrWhatever.MulitDock="{src:FlaggedEnum Left|Bottom}" />
2. Since attached properties can be of any type, they can of course also be complex types (with multiple subproperties) or even collections, so it is easily possible to do something like this:
MyCustomPanelOrWhatever.SetMultiDock(new List<MultiDock> { MultiDock.Left, MultiDock.Bottom });
If you have defined your attached property that way, you do not need any converters for xaml, you can use it directly:
<CheckBox>
<src:MyCustomPanelOrWhatever.MultiDock>
<src:MultiDock.Left/>
<src:MultiDock.Bottom/>
</src:MyCustomPanelOrWhatever.MultiDock>
</CheckBox>
I've run into a puzzling limitation in a Silverlight 4 UserControl.
What I'm trying to achieve is to have a panel, which slides out from a minimised state when a button is pressed, but the title bar of it should be draggable with which this maximised state can be resized.
What I've done for the sliding out is to animate the MaxHeight property of the parent Grid of this panel which works quite well even with no hardcoded Height for the panel, but I don't know how can I make this dynamic.
Trying to bind a variable from the code-behind to the 'To' parameter of the 'DoubleAnimation' didn't work, it just silently gets ignored.
As I'm creating UserControls to represent Views, the elements with x:Name properties won't get autogenerated.
I tried to work around this using the code below which mimics what happens in the autogenerated code (with the added bonus of only being done after the layout is actually loaded):
public DoubleAnimation PanelOpenMaxHeightDoubleAnimation;
private void LayoutRoot_Loaded(object sender, System.Windows.RoutedEventArgs e)
{
var LayoutRootreference = sender as Grid;
PanelOpenMaxHeightDoubleAnimation = ((DoubleAnimation)(LayoutRootreference.FindName("PanelOpenMaxHeightDoubleAnimation")));
PanelOpenMaxHeightDoubleAnimation.To = 383;
}
This however breaks when trying to set the value of To, as FindName returns null (I have x:Name manually set in XAML for this particular animation to "PanelOpenMaxHeightDoubleAnimation"). I have the sneaking suspicion FindName can't pick DoubleAnimations up from VisualStates, only actual layout children?
I did find the documentation about XAML Namescopes at http://msdn.microsoft.com/en-us/library/cc189026(v=VS.95).aspx#UserControls, but didn't really understand what my options are from this paragraph (other than being very limited):
For the case of a UserControl, there is no equivalent template part attribute convention for parts of the UserControl in the definition XAML, nor is there a template applied at all. Nevertheless, the namescopes between definition and usage remain disconnected, because the definition namescope is defined and then effectively sealed when you package your UserControl into an assembly for reuse. A best practice here is to define your UserControl such that any value that needs to be set to modify the definition XAML is also exposed as a public property of the UserControl.
What does it mean by the last sentence?
Wondering can I do next? Should I try to generate the entire state from code?
Well, managed to work it out so I'm sharing the solution.
Instead of trying to get a reference to the DoubleAnimation in Resources, I named the Grid in the layout I want to animate and get a reference to that using the code in the original question:
var SlidePanel = ((Grid)(LayoutRootreference.FindName("SlidePanel")));
This does return the element and using that it's possible to create a DoubleAnimation and a Storyboard from scratch purely in code. I just used this code example as a starting point: http://msdn.microsoft.com/en-us/library/cc189069(VS.95).aspx#procedural_code
Best part is, you can change the DoubleAnimation.To parameter even after setting everything up in the Storyboard, so now what I'm doing is just resetting that to my calculated value every time before calling Storyboard.Begin().
It's a bit fiddly to set all these up manually, but at least it works nicely once you do.
Databinding in WPF/Silverlight revolves around dependency properties, DataContext objects and DataSource objects. As far as I can tell, dependency properties are the same thing as ambient properties and their significance to binding is basically that if you put a bunch of widgets in a container then you only need to specify a DataContext for the container.
There are several parts to this question.
What is the difference between DataContext and DataSource, and how do they relate?
What manages cursors in WPF/Silverlight databinding? Is there a direct equivalence to the WinForms CurrencyManager and BindingContext?
How do I go about manipulating a Cursor in WPF/Silverlight databinding?
DataGrid seems to have a CurrentItem property. If you bind a bunch of widgets to the various columns of a datasource and they share the same datacontext as the datagrid then interactively moving the selected row in the datagrid changes the row whose values are expressed in the widgets. Could someone please explain to me how it all fits together? Preferably with reference to SL4.
When I do this:
private void buttonNew_Click(object sender, RoutedEventArgs e)
{
Guid newId = Guid.NewGuid();
Employee emp = new Employee() { Id = newId, FirstName = "NOT SET", LastName = "NOT SET" };
AtomDomainContext adc = employeeDomainDataSource.DomainContext as AtomDomainContext;
DomainDataSourceView ddsv = grid1.DataContext as DomainDataSourceView;
}
I get this compilation error:
The type 'System.ComponentModel.IPagedCollectionView' is defined in an assembly
that is not referenced. You must add a reference to assembly 'System.Windows.Data,
Version=2.0.5.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.
D:\Argent\Views\ManageEmployees.xaml.cs, 57, 7, Argent
which sounds easy to fix but when I attempt to add a reference to the Argent project the list of references is empty; presumably one is confined to those assemblies that Silverlight deploys to the target computer. So now what do I do?
I found some answers so in the absence of a useful contribution from anyone else I'll answer my own question.
A DataContext is a kind of cursor object. You assign to the DataContext property any object or IEnumerable collection of objects to which you want to bind, and a wrapper is constructed around it. If you assign an IEnumerable, the DataContext surfaces a CurrentItem property that references one of the elements of the IEnumerable. If you assign something that isn't an IEnumerable, the DataContext wrapper behaves as though it contructs an IEnumerable and adds your object to the collection and then proceeeds as if that was what you passed in the first place, the object being set up as the CurrentItem.
One possible IEnumerable is the DomainDataSource, for which DataSource is a base clase.
Every widget in Silverlight has a DataContext property. Generally you don't set this directly, due to what Microsoft has taken to calling "dependency properties" which as far as I can tell are exactly the same as ambient properties, which is to say that unless you set them explicitly they "inherit" a value from the immediate container, which may in turn so inherit. So instead of setting the same IEnumerable as DataContext on a bunch of widgets, you make them all children of some container and set the DataContext for that, and they all miraculously get bound to the same cursor.
You can create a new DataContext object in XAML simply by explicitly specifying it; this creates a new instance and assigning it to the DataContext property of the widget on which you specify it; this is a new instance, a new cursor that is independent of any other DataContext.
In Silverlight4 you can reference the DataContext in use by another object; see element binding.
But a binding is only partly specified by a DataContext. Having specified a DataContext so that a widget has object foo contributing its context, specifying a binding path of A will look for a property named A on object foo and if this is found will mashall its value to and from your widget.
What's really confusing to the newbie is that while the whole binding can be specified in one spot, normally the context is specified miles away up a big complex container hierarchy, and just the path is specified on each widget, yet for (eg) binding the ItemsSource of a combobox to a lookup table you do specify the whole thing. I hope I've made it all a bit clearer for those following in my footsteps.
As for the location of the elusive 'System.Windows.Data', it's in %ProgramFiles%\Microsoft SDKs\Silverlight\v4.0\Libraries\Client\System.Windows.Data.dll
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)